My rooted phone won't turn on
You most likely bricked it. If you have a custom recovery installed, (Hopefully you do) you can unbrick your phone by booting up into it and reinstalling the stock software. Can I ask what recovery (if any) you have?

If you have TWRP you can navigate to: Wipe > Advanced Wipe then wipe cache, dalvik cache, data, system. Then navigate to: install/flash then navigate to where your ROM is and flash it.