I'm a support main, and sometimes I get ADC in my games. I'm pretty bad at every other role, so I usually just pick Ezreal or Twitch in my games. I pick primarily Ezreal just so I can ignore my support and be safe while farming.
As a top lane main I hate every role except support. When I want to win or do well I put my primary as top and secondary as mid. When I get mid I'll just pick Aatrox and do anything but die. The peeling thing naturally comes with top lane and trying to protect my squishy teammates. If you haven't given top a try yet maybe you should?
learn to play jungle as a tank, its very simple and your job is still to peel, gragas is a good pickup
I play a champ I feel like playing that fits the role
As sup primary and bot secondary, I've largely been playing ashe when I need to bot (which is like 1% of the time). I figure she provides utility even if I do poorly, and that way I can leave the damage to people playing their primary role.
I do primary bot in normals and on at least one of my other accounts though, so I probably should be playing stuff like luc/cait since it's not like I'm bad at the adc role, but being spoiled by all support all the time makes me wary that somethings gone wrong whenever I don't get it.
I have no idea what it's like to get my secondary role yet. I queue up for support/jungle and I've gotten support every single game.
I haven't played ranked yet (because I get super anxious) although I might get to it soon (about to finish my degree will have more free time). I am considering whether to pick Support/X or whether to pick Fill
Part of my problem is that if I were to get a role other than support is that I lack the versatility, so rather than not being able to play another role it is that I can play one champion in those other roles it gets picked of banned and I am in trouble.
The most glaring example is if I were to go top I am going to struggle with anyone other than 
... I guess I could scrape by by playing one of my mid champions 
.
In mid I am not too bad, but I am basically playing support but with gold, I may have trouble against assassins and aggressive opponents... but I will struggle to be the damage source should my team need it.
In jungle I am not practiced with meta champions... no adc jungle for me.. I still play tanks... including (high ban/pick rate) my favourite is 
with her game changing ulti and cute poro rider skin. I feel like this would nominally be my second pick as its a role i tend to get a lot in normals.
As ADC I can play 
really well. I am not sure why but I have been struggling recently with 
and 
. I can't seem to last hit with her auto blergh. I'd be worried if my support is too aggressive or bad to protect me in lane.
Learn another role, it will take awhile and mightn ot be as fun for a bit, but trust me, learning a secondary role is needed if you are eventually going to dive into ranked in the future. Support/ADC is a good combo because you already see what the adc does being a support main, so you already have knowledge of it. Just need to learn the champs, and what each champ's role is, because they are very different.
Learn to play your secondary well so you don't have to worry about getting it.
