My Roper elictric dryer is not drying clothes

If you are experiencing longer dry times and/or poor drying efficiency, the following link can give you some tihings to check before assuming there is a malfunction with your dryer:

http://www.fixya.com/support/r3578821-dryer_takes_too_long_to_dry

The number one cause of dryer heat related problems is poor exhaust ventilation. If not vented properly, a dryer will not dry efficiently, will take longer than required to dry, and will cause the heating circuits to overheat to the point of failure. The dryer will actually seem hotter as the heating circuits begin to overheat. This is also the source of many fire hazards if not resolved. Read through the link provided and review some of the potential causes. Hopefully, this may save you a service call. If you check everything and still have poor heating issues, please let me know. You may have an internal bias or hi-limit thermostat malfunctioning.

Good day,
If the dryer keeps running the entire cycle (you have to be there to be sure) and the heat stays on the entire cycle, then remove the vent hose from the back of the dryer and see if the air is is coming out of the back forcefully. Plugged dryer or vent pipe could cause that. and did you check to see if it's actually tumbling.
If it's not tumbling, then you have a warranty claim with the selling dealer, the machine carries a one year warranty.
In fact, if it's not dirt, either in the dryer or the venting system, warranty will take care of the problem for you.