As long as there is some decent demand from their players about specific altcoin then they would be glad to add that their site.
The only one that know which is the best course of action that they should take is the team themselves. They know the situation of the site much better than everyone else. It should be easy to add 1-5 altcoin instantly just like any other site out there but if there isnt any interest from their players regarding those altcoins then it would be the same as wasting their resources.
Some site has survive the competition so far by offering only btc and some only offer 2-3 or altcoins instead of tons so Roobet offering BTC and ETH on their site should be good. Also they have been relocating their resources more on promotions in bitcointalk and its pretty good if you compared with some other site.
When trying to finding some pictures from "Guess The Slot" already trying a few VPN from America, Netherlands, UK, and still got a restricted country from the slot provider. Then, decide using a review website to see the restricted slot for contest purposes.
Let me tell you the magic country , try India . Still got few restrictions on some slots but way less compared to the others