I do regularly participate in twitter contests and giveaways from casinos I trust like roobet, but winning those contests is very rare. Yeah, I guess it's a waste of time. But I have won some contests in other casinos like in Stake, I've never experienced winning in Roobet's Twitter contests and giveaways hopefully soon since this day they regularly posting contest. However since I started joining their art contests here in BitcoinTalk, I think I've only not won twice from the day I started participating in Roobet art contest here in BitcoinTalk.
If you have won some times already (even though in other casinos) than it is worth your time. I never participate in such a contests as you have a lot of bots and multi accounts also trying to claim the bonus,sot I prefer to skip those. Congrats in winning a prize in the art contests, I always check all the subscriptions and we have a lot of talented people on this forum!