Can i unroot my galaxy ace to reclaim my warranty?

I want to root my device to install apps in sd card cause my internal memory(181mb) is getting ful.My android version isseeing in boot loader,,and i don't want my device to be without warranty and at the sometime i need to store and use many apps..so i have to root my device!!..perfect unrooting is possible to reclaim my warranty!! 2.21,baseband version is s5830DDKC1,Kernel version is 2.6.