What happens if you dont kill roman in gta iv?

The fate of Roman depends upon whether you choose "Deal" or "Revenge" towards the end of the game. If you choose "Revenge" then Roman will survive and go on to keep contact with Niko. After completion of the final mission, Niko gets a phone call from Roman who tells Niko that Mallorie is pregnant and if it is a girl, they will name it after Kate.