Am using Samsung Galaxy Y model phone. I rooted my mobile and installed Jelly Blast v3 ROM in my phone. Now how to install a different custom ROM over this ? or if i install a new ROM in my mobile will that cause any problems ? Please help me get through this
You need to install custom recovery and flash new ROMs from this recovery. If you choose the correct custom ROM for you phone and follow the developer's installation guide, there won't be any problem. If you wanna know where you can find custom ROMs for your phone, take a look at this question. I recommend XDA developers. You can find a lot of ROMs with user's reply so you can consider before flashing the ROM.
If you are already rooted and using a custom rom you probably have a recovery installed. You wont have any problem if you change the rom but make sure you have made a nandroid backup before doing anything so that you can revert back to your current state in case anything goes wrong. Choose the new custom rom wisely and follow the instruction therein and you will be alright.