I would guess that it is not really an idea for just one time marketing, but at least "some" marketing. We haven't seen them doing marketing for millions and it looks like maybe they won't do that at all. This is why I believe that they got the money and did absolutely nothing with it.
What sort of marketing / promotions are you guys really expecting? I mean if you guys do want to see something then simply ask for it. Rollbit's staff are pretty much open to what the community wants though. They are not active in this forum so hit up the discord channel and write all the stuff that you want as part of the suggestion if you truly want that
I would guess that the best one right now could potentially be wagering competition. It could be profitable for them, or maybe it won't be but they would have the money for it. So something like "biggest wagering competition!" type of deal with 100k reward would mean that they could get 100k while people lose to win that reward, or maybe they won't, but they would be able to afford 100k even if nobody gambles, and it would be a good one.
On top of that, pay people A LOT here for a month leading to the end of it, and that would get a ton of marketing here as well, and maybe twitter as well, pay influencers to retweet or post something about this wagering competition. Basically a competition + marketing to get that heard.