How are you supposed to practice rolls/champions you're not good with?

I know match making 'apparently' is adjusted for rolls and champions you're less familiar with, but tbh I always feel like I'm facing people of a similar skill anyway.

So I ask you, how are you supposed to practice with champions or rolls you're not very good at?

I'm currently trying to have atleast one or two champions I can do well with in every lane, (I normally main support), but taking anyone I'm not used to in top lane or ANY ADC means I just get absolutely destroyed in lane. Not just lose a little, but lose such that after the first time I die, I feel like I can't practice anything but last hitting, and this happens every time I try.

I've practised against bots, and win easily every time, but I how do play against people of a similar skill on one roll when you're ELO is much higher in general? Currently i'm silver, but i'm probably a bronze when it comes to adc because they work nothing like the fighters/tanks I normally play, so how am I supposed to practice and get good by just being face rolled every time?

Any one else have this problem? Or should I just stick to the same champions in the same rolls, because however I try to play different ones, you can't practice against people of similar ability that you are with champion x. You have to play people as if you're playing someone you're used to the mechanics of all the time, even when you're not.