As far as I'm aware, you can make any kind of campaign you could imagine! I haven't heard of anyone being turned away -- some folks even use Roll20 to play board games. I think the sky's the limit. If you haven't checked it out yet, the help docs should go a long way towards explaining things. I would especially watch the GM overview and/or Player overview depending on if you want to run or play in a campaign. If you're not sure yet, I suggest starting with the player overview to get a quick rundown on how the site works. Character creation can be handled however the GM and players like. The app is pretty system agnostic, so it shouldn't trip you up. Certain rule sets are tough to replicate, of course, when they have really unusual die rolls and things like that. If you're looking to join a game, go check out the "Looking for Group" forum here. Lots of people are searching for players and DM's for all sorts of games, so don't be shy. If you don't see anything you like, you can always make your own post to see about drumming up a group too.
