I have never used Roboform but I did just visit their site briefly and it referenced entering a master password.Quote from Stealth Trader:
Once roboform is setup, you do not enter any keystrokes from that point on. I'm not saying it's Fort Knox secure, but the chances of anyone breaking through it to access the average traders account is remote. There is a difference between being paranoid and sensible.
If you have configured Roboform not to use a master password then I can only assume that your Roboform password file is not encrypted and would be easy pickings for a trojan to steal.
Look, I'm not saying that Roboform is or isnt a good idea. But the idea that you can live with a trojan keylogger on your machine and not worry about it is delusional. Once its on your machine you are likely screwed.