What is role of DPS/Tank?

Ive reached grandmaster lobbies (solo queue) using primarily support. Im a strong support player and can flex all the support characters, but when it comes to team comps, we've all had our fair share of the people who dont want to swap. The moments were I queue with 3 support mains can be hell because neither will switch, including me. I want to be the change and be able to play all roles but I'm not confident in tank or dps because I'm not certain in the goal/job I should be achieving. I try to practice the roles in QP but the lobbies are full of terrible players where I can get away with almost anything.

For dps, spidey, magik, and bucky instantly click for me

And for tank Im only good with Peni

I just want a foundation so I can improve and be flexible for my teammates in ranked so we can get the dub, but I understand how nuanced both of these roles can be, so I'd appreciate some insight from strong players in these roles