Dominique is correct. Both can work.
In terms of SEO the question would be ‘is your primary site have any age or Page Rank?’.
If so you can use that to make a much bigger impact, especially if you are going after a Hollywood term like your example ‘roulette’.
You also have the option of building a subdomain rather than a new site (which would be very difficult to get ranking). Something like roulette.yourwebsite.com. If you link to it from any page (but preferrably your existing homepage because that carries the most influence) the benefits would be passed on immediately.
This is significant because typically link values deteriorate with each link that points off of the page, even if it leads internally. This doesn’t happen with subdomains.
Although Google sees the subdomain as its own individual URL/website, it also recognises that it is a subdomain of the primary URL and treats it like a second level directory off the index page when it passes rank.