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.
Winning prizes in art contests will have better chances even though this requires certain skills, compared to taking part in giveaways on social media held by Roobet or any other casinos because the competition is different.
In art contests, if you have a very good artistic touch, even though there are competitors, there is a chance for you to win if the Roobet team likes your work, especially if there are not too many competitors in the contest.
But giveaways on social media are just based on luck, even if you have to guess something, the chance is still small considering the number of people who take part with the prizes provided, but because this doesn't require any skills, we can take part at any time because the chance of winning is still there, just don't know when we will win the giveaway.