The cookie-clearing option you suggest has also been tried. Didn't help solve this problem. Also, I tried to access Roobet.com using different browsers. Nothing changed. VPN was not originally used, but was used as an alternative and see if the access problem can be solved in this way. Also to no avail. All of these were tried long before you suggested them. If I knew the solution, I wouldn't be asking here.
Sounds strange. I even don't have any minor issue with connection to, and loading on Roobet. Obviously it is for today. I am not sure how it was in previous days. Some people said the website had some issues, lags a few days ago. Perhaps you got such in lagging days of the casino. Have you ever tried to contact Roobet's support?
There's a problem on image loading to your browser base on your description that the website is only showing a fragment of the casino display. Do try to clear the cached images and files? Your browser might be loaded by heavy cached files from different website that result on this slow loading. Roobet website has a lot of image to load on there homepage, This might be the reason why you are getting this error. You can't access the website even the glimpse of it when using VPN if you able to load some part of it. Cache image files is my prime suspect for your error.
It can be problems from cache, VPN or unstable, limited Internet bandwidth from users. I don't have problems to connect to Roobet and loading process works fine for me. I try with some browsers and they are all working fine with Roobet.com. Of course, no VPN, no Tor. Furthermor, from what you said, I believe it is not issue from Roobet side, but from user side.