Brake Help needed

[sarunas4]

hi guys, I got myself into a little mess... my brake sensor warning went on.. so i checked the brakes, the pads were gone, the rotos were still thick enough. so i got new pads, left the rotors as is. not the car vibrates when i hit the brakes at higher speeds. its been about 5 months and slowly its getting worse.
So now i decided to change the rotors to try and get rid of the problem, my question is do i need to change the brake pads too? Theyre still thick, but since the rotors are new and the pads might have wear from the old ones they might now fit on the rotor properly?? or will they wear in and even out?
thanks for any help