Ehh... 2nd attack requires investment of starting off with Budew instead of just Roselia, so you really can't rate this card without seeing Budew at the same time to see if it's really worth it. Without Budew, that attack is a bit "eh" and surely there's more powerful stage 1 out there than 3 energy for a plain old 50.
Weak to fire isn't very good, as fire Pokemon got some pretty high damage output. One retreat cost is average and acceptable, same with the 90 hp for stage 1.
Poison Sting is quite a reliable attack, but it's not anything really good in particular either... strong, fair, but not game changing or game ending.
7/10
(scores will change depending on Budew's card)