I was wondering is it ok to undergo root canal when I have slight fever, I also have sinusitis?

Depends. It depends on whether you can breathe through your nose, and how bad your fever is. Of course it also depends on how much pain you are in. If you are not in severe pain, you should wait until your fever is better. Your sinusitis may be cause by an upper tooth that needs root canal treatment (if your root canal treatment is to be performed on an upper tooth).
Preferably wait. If you are in pain, then i would say yes, however, if you are not in pain, then i would recommend you get the fever and sinusitis under control prior to having the root canal. You need to find out if the fever is related to the tooth, the sinusitis or something else.