PA-32R pilot reported an engine malfunction during departure climb. The pilot decided to return to departure airport and landed uneventfully.

Narrative

Aircraft X departed runway ZZZ for a local VFR flight (ZZZ-ZZZ1-ZZZ)). Take off roll was normal with gauges indicating full power as expected. Initial climb rate was about 7-800 FPM but quickly depleted by about 800 feet AGL. Engine was running smooth and indicating full power. After a short discussion about the abnormal flight condition; both pilots agreed and opted to terminate the flight and return to ZZZ. We did not [request priority assistance] at this time however did request to maintain our current altitude. A short time later pilots observed an un-commanded change in the engine performance characterized by sudden momentary roughness. As a precaution Person A [requested priority handling] with approach asked for vectors back to [Runway] XX; but had the runway in sight and turned for it immediately. Tower advised that emergency equipment was standing by and a normal and uneventful landing followed. Aircraft will be inspected by a mechanic prior to any further flight operations. Fuel indicated well in excess of 40 gallons (2.5 hours or more available flying time).