Need help climbing

I'm an average mid main stuck in Silver 5. I don't like blaming my team for losses, as it's a 5v5 so of course I took part in the loss as well. I'm quite confused on how I'm losing however. So I'm just going to ask a few questions.

1. How does one properly snowball? Although I don't want to sound conceded, I don't lose lane too often, and stomping my enemy laner is actually quite common, but I don't quite know what to do afterwards. I try roaming but usually a lane is so fed that my help wouldn't do much, or they're pushed up so a roam wouldn't do anything. That brings me to my next question.

2. How does one properly roam? Do I quickly just push out my lane and then roam, or roam regardless of whether there are minions in the lane or not? Should I be afraid to tower dive for a roam or just stay mid for the experience. If i have teleport do I tp as soon as a fight breaks out or wait for them to push past where I want to tp from to flank?

3. How do I deal with getting camped? If I'm getting camped to the point where I'm not worth anymore gold and their lee sin KEEPS. COMING... how do I play around it?

4. Should I pick champions that I'm comfortable with, or champions that complement our team but I'm not too comfortable with? If our team needs a good teamfighter but I'm not too comfortable with Viktor or Anivia, should I still play them, or needs more poke but Vel'koz isn't my strong suit, should I stay with my Ahri (I main her)?

It may be a lot, and if you have more tips please say them, but thank you for your time! [slayer-pantheon-thumbs]