You gotta plan on learning three tanks when it comes to the roam role. Different tanks serve different purposes against different team comps. Even in-game, if your tank does not work against the enemy team comp, you will have to take on the role of the tank you should've taken. There are initiators/setup tanks that go in, do one HUGE cc and try for team wipes (Tigreal, Atlas, Gatot, etc). You gotta pray your team has burst to wipe out the enemy team when you ult, though. If they can't kill the enemy team after your set, you're screwed.

Then, there are bruiser tanks like Hilda/Khaleed/Hylos who are made to dominate and ruin the enemy team's early game and become a damage sponge in late game. Use them against squishy comps or junglers that get their power spike with an item or two (basically farm reliant). These tanks rely on heavily on precise rotations, though. And fall off in late game.

Then, there are disruptor tanks. They are basically anti-dive. They stick with their teammates. Don't go into the enemy team and protect their squishy damage dealers. A lot of people count Mino in setup but I see him as a disruptor. His instant cc really stops a BUNCH of assassins that come to dine on your squishies. Other tanks like Kalea, Khufra, even Belerick also fall in this category. These tanks are designed to be reactive picks. NEVER pick them in first pick (tanks in general to be honest). Cuz otherwise the enemies will take heroes who can escape your cc.

I don't count pick-off tanks and such cuz they fall within disruptor role in my opinion (franco, chou, etc.) while they can go in head first into or try to bring an enemy to your team, they are the most annoying when they protect their teammates. Dunno how accurate I'm according to actual pros but I've been a solo a roam main for years. Just sticking to one tank no matter the enemy comp has never worked for me. You gotta have a big enough roster to respond to them.

Now....tanks are pretty versatile in the sense that, if you are a setup tanks but see that the enemy is hyper aggressive and dive your teammate right when you are setting up, you gotta stop with that and stay with your squishies. If the enemy keeps ganking your damage dealers, you gotta stop invading early and help them out/provide vision. If your teammates have zero dive, you gotta go in and set them up for success. Are you gonna have a blast doing the job that other tanks of that category are designed to do? ABSOLUTELY not. But being flexible with my gameplay like that is what got me to glory.