Like me, i'm using desktop and mobile when I gamble and both have their own conveniences, desktop has a wide screen and can give better experience so it's more enjoyable. While in mobile you can play anywhere as long as there's a connection and ideal to those who are often away from home. Moreover, many casinos are mobile friendly so it's not a problem even it has a small screen.
This is built up well and if you don't know, they have to test their design a lot to make sure their UI matches for all screen resolution from desktop to mobile. That is a lot of works from their designers and developers and it requires careful works, deployments and testings.
Maybe it is for me only but I really careful when explore a new site on my mobile. Because we don't know much about their trust and their website can contain hazardous things which can steal our information on screen, keyboard. My mobile is a device I used to store my 2FA so I don't want it to expose to so many new sites.
Rollbit is big and has good trust so we can trust them but my advice is for new sites. If I try new sites, I use my desktop, not my mobile.
The stable connection is essential in both the cases because if the internet connectivity is gone your wagered amount can be lost or the fun part is also missed so be sure to have that in mind.Rest we can enjoy it on any device if the casino has made it compatible on all the devices.
A site performance does not be affected and are not different too much between desktop and mobile. Only UI can be different but if it is designed and tested carefully, it will give same convenience and comfortable feeling for users.
With same Internet connection, you will have similar experience on desktop and mobile. But your mobile device should be good enough and not too old. Over heated mobile device can reduce performance too.