Clear the dryer door of any obstructions between the door and the door switch. Your door in the closed position alerts the Roper dryer that it can safely operate. The door cannot send this signal if it isn't properly closed.
Reset both circuit breakers for your dryer's electrical system in your home's circuit-breaker box. If you have a fuse box instead, check the fuses to see if they are blown or burnt. Replace them with time-delay fuses as necessary.
Unplug the power cord and look for bent prongs or signs of arcing in the receptacle. Ensure the receptacle can support at least 240 volts. A 240-volt receptacle has a three or four-prong setup, with the four-prong allowing for a grounding prong.
Access your dryer's control panel by removing the back cabinet panel. Consult your Roper model's manual for specifics, but access is usually gained by removing four small hex bolts on each back corner and several small ones behind the control panel.
Turn off power to the dryer at the breaker or fuse box. Locate the start switch and timer motor by following your wiring diagram. Test the resistance rating for both by disconnecting the wires per your wiring diagram and checking the readings with an ohm meter. If the readings do not match their ratings per the diagram, replace the respective part.
Look in the exhaust area, which is on the back of the dryer where you connect the vent tube, for the thermal fuse. The fuse is usually flat and rectangular with two thin prongs sticking out. A blown thermal fuse tells your Roper dryer that it's overheated and prevents it from working.