If it has not been updated then it will probably not work. However if you turn on Site Administration > Debugging > DEVELOPER, before you add the last updated Roshnilite theme, you will soon find out if it is not up to scratch. However, you will be pointed to the places that need updating. It may be you need to make some minor updates to various parts, within that theme, where Moodle has made some recent core changes.
If you get stuck just give me a shout and I'll try and help you..
Cheers
Mary