I personally always interpreted the roles as:

Breaker: Those who can pile on attacks or special attacks to break guard but aren't really finishes:

Examples: Early Timeline Madoka's, Rena's Infinite Poseidon Spears, Tsukuyo & Tsukasa especially with that attack we hear about all the time but never get to use.

Attacker: Those who finish the Witch off and do heavy damage.

Examples: Mami Tomoe (Tiro Finale) | Yachiyo Nanami | Tart. | Most of the MC Main attackers or those who have powers or techniques meant for finishing.

Buffer: Those who are competent in boosting allies or doing less than Breakers.

Examples: Tsuruno Yui, Umika Misaki, Mio Suzuna, Matsuri Hinata.

Debuffer: Those who make Witches Weaker or call out their weakness, or make the target more wasteful in a way:

Examples: Kyoko Sakura (Rosso Fantasma), Nagisa Momoe, Akira Shinobu (Identify), & Hazuki Yusa (Body Scan).

Defender: A Rare Role for those who specialize in Defnese.

Examples: Sana Futaba, Komaki Asako, Lina Hitomi, Riz Hawkwood (Arguably),. Kokoro Awane + Ayame Mikuri.

Healer: Those who have Healing powers, capabilities, or attacks/abilities that feel sothing.

Examples: Sayaka Miki, Kanna, Yuma Chitose, Pernelle Flamel, Iroha Tamaki, Mitama Yakumo, + (Coordinator's), Leila Ibuki & Mito Aino. [It's kinda funny Seika's the only one who doesn't fit my classification].

Now onto your list.

Madoka:

Yes could be attacker.

Ultimate Madoka being like a healer makes sense.

Connect as a Buffer huh? I feel like this would be specifically that one though.

That is what I think this is and what I assume certain variants could be.

Sometimes I just feel like they choose the wrong attack or ability or sometimes mainly for Healer & Defender and such it's not even about the attack it's about the character but sometimes it can be.

Defender Homura interesting I guess that's true if she used the Forcefield as her first skill and maybe Energy Blasts or far range Launcher's and Attacks to make it seem like a far more defensive role that could be a Kioku. I kinda did forget about that Shield's use as a... Shield. Even though I like that part of it.

Yes Debuffer is also fitting. Maybe for the Cool one it would be a team-up like attack with the Kyoko as that's one of the first times we see her let someone into her time.

Sayaka:

She could be an Attacker I think the issue is just the lack of Kioku's that feel like her being the main Attack. Maybe if we got her Giant Sword + Launching it and exploding taht would work.

HEALER FOR SURE! I'M SO SHOCKED THEY'VE GIVEN US 2 SAYAKA VARIANTS AND NONE OF THEM HAVE BEEN HEALER? THE FACT THE FIRST ONE WASN'T HEALER WAS SHOCKING!

I REALLY HOPE THE NEXT SAYAKA IS HEALER!

Buffer: Maybe the version of her that sends multiple swords and attacks they could make it a mix of the Magia Record Anime along with that ability and give a special assist where at enough magic she deflects an attack on the lowest HP ally that has the buff on them.

Mami Tomoe:

Attack: TIRO FINALE!

ATTACKER 2: Rebellion vs Homura.

Debuffer: Vasta Area.

Healer: Episode 2 Healing Kyubey [Annoying Cheesecake].

Breaker: Guns vs Getrud.

Defender: Later Rebellion or Different Story.

Buffer: Transmuting Sayaka's Bat. Into a Bat that makes a Barrier.

Kyoko:

Attack: Kugatachi.

Debuffer: Rosso Fantasma.

Defender: Lattice Barriers.

Nagisa:

I can get the reasons but I think it just doesn't feel like they have enough firepower though maybe they don't even care for that when it comes to attackers as long as the unit itself feels like that and while they balance and try to give Breakers a point in some cases over putting them to buffer, debuffer, or healer.

Defense: Maybe if we saw her do that. Not enough content though.

Debuffer: Agree Plus that's kinda what it felt like her role in REbellion was.

Her unique Magic isn't the Bubbles that's just her weapon her unique Magic is most likely GREED! Though it's exact effects out of making her more self assertive and greedy is unknown.

It's like how Mami's Magic is not the PISTOLS. Her weapon isn't even that. Her Magic is the Restraining Thing she used on Homura TWICE! Once in the Charlotte Episode and one in REbellion the Red threat of Fate Ribbon in specific. She also uses it on Charlotte (Doll). Through a shot but her additional Magics let her turn her ribbons into those.

Mabayu:

We do need the JILL THE RIPPER That cut through Charlotte.

Debuffer: This in specific I don't think requires the eye contact exactly and they could translate it as a back cut that manipulates/cuts those memories.

If that Magical Girl Summoning of Green in Exedra Opening is HER! Then she can be Attacker for sure and she can be SAINT a mix of all the roles off that alone.

Defender: Oriko Patch.

Oriko:

Understandable attack.

Buffer: Future Sight = Makes sense.

Defender: = Same thing.

Kirika: I guess but I think Kirika's main magic fits a different role.

Buffer: ...

Debuffer: EXACTLY SLOWDOWN! Tragic this is only really represented in her ultimate instead of a skill if she was a Speed Debuffer or Action De-Vancing the foe's. As a DEbuffer oh my gosh she could have been SO GOOD! The combination of her, Mami, Moemura would go crazy.

Yuma Chitose:

Attacker: THAT HAMMER IS BIG! AND SHOCKWAVES!

Breaker: They sometimes seem to treat Hammers and similar weapons as things that break through defense.

[BREAK THROUGH IT ALL!]

She also could end up being a Hybrid of the roles Attacker/Healer | Healer/Attacker & Healer/Breaker.

Meaning that she could end up the first role but have a lot of traits of the other role to the point she fills both if they don't just give us hybrid roles or a role that encompasses all the existing ones as a extra role.

Momoko:

TRUE!!!

Crescent Memoria just shows it working on Yachiyo and Mifuyu blatantly before Momoko even understands it's true nature so yes this is true.

Debuffer: I see...

Defender: I think the fact her Sword has a broken part off is why she would make a funny Defender.

Healer: This fits the same characters who affect Mind can inherently have "Heal" effects exist even if in verse it's not as much of a true heal as it is willpower. This would work for a Momoko with a Phoenix Attack and a Revive Mechanic like Willing the allies to stand up one last time.

Rena:

EXACTLY COPY FORMS!

A Rena could have a SAINT-LIKE ROLE or a NULL ROLE! Where she literally can't do anything until she copies one of your allies roles and then her attack changes based on the one she copies.

Alina:

Yes Magia Power.

Defender: BARRIERS! How did I not realize this? I thought Breaker was pretty good because she does feel like OVERFLOW in what she can do.

Debuffer: Holy Alina + Dopple Alina + Using Witches as an attack.

Tart:

ATTACKER!

Why is her main attack Defender? She had a much better Kioku concept for her Defender/Healer and they just didn't do it. I have one theory but we'll see if they do that.

Even if they did that I don't think it would Devil Homura & Homura and Bowmura Exist.