mid laner here: I hate supports who endanger their ADC even if it's to gank me, help their pre jungler, or freaking waltz across the map for an entire minute just to gank their top lane pre. I understand roaming, but if A) the ADC can't follow or B) the ADC is against a hard engage / tower taking enemy and already having a hard time, letting them become completely useless rather than slightly behind puts a lot of pressure on me to deal all the damage, and makes it hard for me to roam when bot lane is 1v2 and it's completely dependent on top lane's wave.
It also makes me have to rush void staff unless there's super strong and reliable physical damage elsewhere, denies first turret gold, and leaves our own jungler having to either defend bot lane or power farm to make up for the ADCs lost gold. Finally, dragon is key and losing both first dragon and first turret is hard to recover from even if I get a triple quadra kill mid lane somehow.
When I play support, I freaking roam mid constantly, but I make sure my ADC is either backing, freezing lane, or long ranged against short ranged (and no blitzcranks). And I make sure I have good CC and base damage, with mobi boots.