since this site is still new
it's good to know that even new you've already focus on the promotions side
Rollbit is not a new site, If you search rollbit on youtube you can check that some gambling streamer / youtuber has been promoting them since last year. I've found a video that was 11 months old about rollbit, some older dates video probably exist as well but back then it seems Rollbit only has those csgo skins type of roulette but now the site is packed with 3rd party slots already
Is there any to test on your site for free? 
It seems no demo mode available in rollbit( cmiiw ) but those are mostly 3rd party slots that other sites have as well so you might want to go to another site that provides demo mode for those slots , if that helps
@Rollbit : goodluck in bitcointalk