It's no problem if you don't get your ADC fed enough. Breaking even is much better. Laning phase is important but it doesn't make or break games. Instead the teamfights is where your team needs to shine. After I climbed to Diamond on my main, I quickly got a smurf from a friend who doesn't play league anymore (Bronze V), and in a matter of months climbed up to plat. Even at the plat elo, people still make mistakes during teamfights.
Roaming depends on what you based your team on and how the game is going. If it is still early, and your lanes are doing fine, then why roam? Only time you should be roaming as a support is to possibly make a play midlane or on the enemy jungle. Besides this, it is important to ROTATE. Especially as support, you need to keep your eye on the map. If your jungler gets invaded, quickly ping it, and move to help him. Don't sit in lane and watch him die. If there is missing enemy zed. Tell your mid laner to follow him. If your mid laner is capable of doing so, and you have a play in mind, quickly rotate up and cut him off. These are common sense things that you should be able to do.
I agree with you that when you're behind the game gets harder. But each game is different and no one is able to tell you what you should do. Just improve the way you play. Be more aware and take calculated risks. Know your exact limits and hopefully you will get good teams who think the same way you do.