My biggest problem with roaming as a support is missing xp. This has been my current worry lately, not falling behind in levels, mainly because I usually play tanky supports like Ali, Thresh, or Taric. If I'm on a caster I don't mind it as much because they exist for their kit's utility, but a tank support has to survive being in the fray and a 2 lvl difference is huge in lane.
I worry about back times and even going to place wards, I'll have to look at it a bit more...