Are you close enough to campus to talk to the Greek Life (or whatever it's called on your campus)? That way you would learn what would be expected of your sorority.
Get in touch with whomever would be the sorority's chapter advisor. Is there an area alumnae chapter?
As for a free Roberts Rules of Order, try your library. You could look at it and get a feel for what is expected. Then when you get elected, you could buy one yourself, but shouldn't the Chapter have one so perhaps the Chapter could pay for it?
I think that this website will have just about any situation ever experienced, lol. If not, ask!
Try the posts by brookelineu..she's written about a fictional sorority..
Good luck!!