Generally, I do not support MS students on research assistantships, but teaching assistantships are sometimes available through the Computer Science Department and you can remain on undergraduate financial aid for a 5th year if you are enrolled in the co-terminal MS program.
If you are interested in doing an MS thesis in my group and if your combined CS and Math GPA is greater than 3.4, then send email to trink (AT) cs.rpi.edu with the following content:
I will review your materials, contact your references, and then contact you.