Rough like vibrations? Or does it surge faster & slower instead of a steady RPM?
If it vibrates, maybe it's the vacuum-operated front engine mount. Wanna check it out yourself? It's front & center, labeled #9 in the picture below.
There's a vacuum line #16, #17, & it somehow connects over to a solenoid valve in the box labeled E-3. (My 2003 was a manual tranny, didn't have the vacuum-operated mount, so I don't know exactly where that solenoid valve is located.)
Get the car warmed up, have someone in the car, with the engine running. Put it in Drive or Reverse & hold the brake. Unplug the electrical connection to that solenoid valve. That SHOULD make it real rough. If not, then the mount isn't working properly. Let us know what happens, & then someone can figure out what to check next.