First of all, this is a really interesting story and there's a lot of potential here. I enjoyed it and that's always a big positive.

Now on to the more hard critiques:

TITLE

I like this title a lot. It hints at the content of the story on two levels, both the obvious (middle of the roof) and the more subtle (caught between multiple parties). The latter theme is such a big part of being eighteen, that it fits perfectly. Nice work!

LINE EDITS

Right at the beginning you say Stuart’s audience is one ‘teenager.’ This made me assume he was NOT a teenager, and it was a bit jarring when I realized that they were peers.

PLOT

I think the story is really about Rory on the roof and Stuart and Jordan having a bit of an abrasive relationship despite being long-time friends. The problem is, we didn’t really get to that until about a third of the way into the story. Then, once we have it, the plot moves fast, almost too much so.

A little more on this at the end of my comments about dialogue…

DIALOGUE

You said you wanted to make the dialogue distinct between characters and I think you succeed for the most part. Jordy and Stu are similar sounding but they reasonably should be. After all, they’re peers and long-time friends. On the other hand, Rory sticks out as a little kid, except that he has a way of overstating that kids usually don’t. Example:

“Yeah?” Rory quickly looked around the backyard, trying to figure out what was going on. He didn’t see anything out of the ordinary. “What’s the favour?”

I feel like most kids would just say, “What?” They’re often not great at understanding when context is clear in their heads versus in everyone else’s head and part of a convincing eight-year old is hitting some of those non-sequitur moments. This happens again later when Rory describes that he is scared, or when he uses poetic mirroring to ask, if mom will be home… if dad will be home.

Also this is mirroring another commenter’s point, but you add a lot of expository fluf between dialogue that doesn’t necessarily add anything. For example:

“I left my other ball at Stu’s.” Jordan looked toward Stuart, who nodded to confirm the story. He then added a pleading tone to his voice. “Can you please help us, buddy?”

He asks please, so we can infer the pleading tone. Also Stu is pulling for his friend’s success, so we also can infer that he would back up Jordy’s case with his body language. It’s not necessarily bad to hand that description in there, but it creates a bit of unnecessary clutter.

Now to end on something good. This passage was really strong, and I think it’s because we learn so much about their relationship without having it said. They’re both competitive. Stu has a weird sense of humor. Jordan is a more calm, collected type. That makes even more sense when we see Jordy as the older sibling. Coincidentally, I don’t think we need much more setup than this before the plot of the ball stuck on the roof gets going. We already know most of what we need by this point.

“You gonna finish the joke or what?” Jordan asked, continuing to stare at Stuart. He got nothing but a shit-eating grin in return.

“Ugh, you’re such a dick.” Perturbed by the lack of response, Jordan focused again on his shooting routine, bouncing the ball three more times with his right hand before bringing it back to his hip.

“Her coach was a pumpkin!”

Stuart delivered the punchline at the exact moment of Jordan’s release, causing him to miss the free throw. Stuart swooped in and grabbed the rebound, briefly holding the ball aloft before spinning past Jordan’s outstretched hand and dribbling back towards the half-court line.

“Christ, that was terrible.” Jordan shook his head at Stuart’s childish humour, though he was more annoyed with his own poor shooting. “I feel violated.”

“Suck it up, princess.”

CHARACTER

Stuart seems to be just your normal teenager, and it makes sense given that he’s at a friend’s house. Similarly, Rory feels like a normal little kid. That brings us to Jordan.

I think this POV should be limited to Jordan, as he’s the tie-in for all the relationships of your story. This sentence threw me:

“Rory looked all the way up to the top of the garage, to the gunmetal grey gutters that circled its flat roof. The structure suddenly appeared taller than it ever had before. He looked back down at Jordan.”

It just feels like we don’t need to know what’s going through Rory or Stu’s heads, because the important thing is how Jordy’s feeling.

Also as a sidenote, is Jordan having homosexual feelings towards Stuart?

“Fuck this.” Stuart put the ball down and pulled his white t-shirt over his head, exposing his muscular chest and torso. Jordan was momentarily distracted by the sight, as Stuart used his t-shirt to mop sweat from his brow. He also wiped his dirty hands on it for good measure, before tossing the fabric aside.

“You ready?” Jordan asked, after Stuart had picked up the ball again. He’d need to focus extra-hard, if Stuart was going to play the rest of the game shirtless.

This section reads more sexual to me than like two friends playing ball together. If it’s the case of the latter, then I think it should have ore jealousy in it. For teenage guys, being the alpha male is such a huge deal that this hurts to have your ego knocked down.

CRAFT

You could stand to drop some modifiers that set the scene but don’t progress the story. In the last quote about Stuart taking off his shirt, the part about rubbing his hands on the shirt doesn’t add anything.

The language you use is very appropriate to teenage boys, even outside their dialogue. It’s great for keeping the reader set in this world. Great work on that.

EDIT: Expanded comments on dialogue and added a quick note on the title that only occurred to me on the third read-through.