This is an interesting topic, because I was told that support is supposed to roam. As it was put "You're not just some ADC's support, you're the whole team's support". So, I guess, if things start going poorly, support is supposed to roam to a stronger character in attempt to swing the game back into your team's favor. ***Credit to CurS1VE for the reply
"I would say if your ADC is behind and lost turret and is constantly pushing up past river or even to river without that Turret (tier 1) then they don't know what they are doing, they should have already rotated to somewhere else and if they haven't (unless ppl are dead on enemy team) then they are just clueless and you are better off leaving them cause I guarantee ppl will come for them, there are things in this game that are just easy kills, nothing is easier than a ADC who is way behind without a Turret. Even if you are a superb Support it's just one of those things that it's almost impossible to consistently outplay.
Also you support the team not just some ADC; your goal is to support the person who gives you the best chance to win while also setting your team up to make plays through objectives that give you the best chance to win."
All I'm getting out of this game is that it's pretty freakin' complicated in some areas (or at least gives the impression of being complicated), and communication is key.
I'm not trying to rag on anybody, because, again...complicated game, and "what you're supposed to be doing" isn't exactly crystal clear at every single moment of the game, but I think a lot of the issue is people play Team Deathmatch instead of "Take The Objective". They don't play around item power (even I'm guilty of sitting in lane WAY longer than I should...which allows the enemy to base, get stronger items, and come back to kick ass). If you have an enemy down, it's probably better to base and get items so you can at least try to match whatever item power spike they'll come back with.
I could be dead wrong, and I'd love the correction should I be wrong, but I'm fairly certain the importance flow chart looks like this...
CS > Objectives > Items > Not Dying > Kills