Hi,
If you will configure uri_path then you will need to change apache configuration.
So in your example uri_path should be empty.
The problem is just that rubycas can't find css/js/img.
I remember that we had exactly the same issue in the earlier version.
It was related with bad sinatra config.
Do you use the latest one from git, what version?
Please make sure that you are working on the latest one and check logs where he try to find those files.
Because maybe this is related with apache configuration not rubycas itself.
You can also verify that by accessing cas without apache just run it and go to url with port and check if you will get css/js/img.