It's never a good idea I think because it will force users to join the site. I don't think many will be interested in such an approach. I barely use a lot of sites, used to be sticky with stake back in the day and now have switched to another. I would possibly join but still would be less interested.
It also can cause problems because some users may not access Rollbit. Some gambling websites in various countries is often blocked because local laws and regulations. For example, I can't access most of popular foreign gambling websites without changing DNS.I don't mind if this is a consideration for Pot B games to Rollbit sites will still follow the existing rules.
I have been using Google DNS 8.8.8.8 for many years without any hassles. It works for Rollbit as well.
And there is no need to change it back to your local Internet provider.