My pregunta is, what happned to Romana? I mean if Rassilon is/was president at the last moments of the Time War EoT pt2. What happened to Romana then.

I think Romana was the other time lord who voted against Rassilon and was the other one who had their eyes covered.

I think Romana could still be traveling and trapped in E space. Though E el espacio is small compared to our space, she had alot of work to do. Besides, with the destruction of the Gate, I don't know if she could leave E space. If she is stuck in E space, it is logical that the Doctor could not sense o feel her exsistance.
As for Rassilon, the Timelords, in desparation must have ressurected him from his tomb. (as in Five Doctors) We know he was the most powerfull Timelord. Also, in "The Five Doctors", Troughton tells the Brigader that no one knew the exent of Rassilon's powers o if he was really dead. Once alive, a vote would be unnecessary. Who would challenge him?