Ive been receiving a lot of promotions via email lately and I guess, they increase this option to those who are not that active playing on their site.
If you use one email for registration on many casinos, it is good if you can label emails from different casinos. You can know what emails belong to what casino and can quickly check them out or skip them if you don't like that casino promotion.
If you are into bonuses and promotions, following the social media account of Rollbit is also a good idea, they gave a lot of bonuses already and on every platform they are trying to share a different one as much as possible. Every site right now is doing their best to attract new gamblers and to retain their old players, having a promotions can be a big help to them.
Following their Twitter and of course following their announcement thread in Bitcoin talk.
Twitter:
https://twitter.com/rollbitcomDiscord:
https://discord.com/invite/Mwx3zqHThey have Facebook and Instagram too but I believe with Twitter, Discord and Bitcoin talk, it's enough.