There may be a hardware issue causing the problem. If however, someone changed a setting while it was in rommon mode, it might not be able to get back to booting normally until the setting is changed back.
The following link:
Is to a page on the Cisco site regarding a 2600 router (what I messed the password up on and had to reset to factory defaults in order to get back into the system....lol) that details how to enter rommon mode, what settings to change to reset it etc.
If you give it a quick read, it'll probably explain a few things. However, you will need to find such a sheet detailing what to do on the model you have.
If not a hardware issue, then it's entirely possible if you reset it to factory defaults and restore the most recent "good" configuration of your router, it will be back to working as it should. If someone accidentally made a change in the wrong register value it will keep going into rommon mode until it's changed back.