CRJ-900 pilot reported a landing gear disagree message after takeoff. The landing gear was successfully extended by using appropriate checklists; and the aircraft subsequently returned to the departure airport.

Narrative

I was pilot monitoring and the FO was pilot flying. Shortly after rotation off runway XX R at ZZZ; we received a gear disagree warning message at roughly 600 ft. I ran the QRH; It lead us to turn eventually put the landing gear handle in the down position. This seemed to have cleared the message. We also were able to confirm that at least the nose gear was able to cycle back down. As per QRH we deliberated with dispatch and elected to return back to ZZZ. Also as per QRH we made sure the landing gear handle was in the correct position; hydraulic 3b pump was on. We let ATC know that we wanted to return. We notified dispatch that we decided to follow through with heading back to ZZZ. We then talked to the flight attendants that we were returning to ZZZ and to take care of anything they needed to be done. We were below 10;000 for the majority of the flight so luckily they didnt even have time to get out of there seats yet. At this moment we have not elected to declare an emergency. As we were starting our descent; atc queried if were requesting any assistance and we asked if we can have trucks standing by just in case there was an issue with our landing gear. Since we were already at 4000; i elected to not call the fight attendants back which in hindsight i should have did a more thorough briefing on my end to them. We did confirm that the flight attendants were seated and the cabin secured. We proceeded with a normal landing and parked with mx waiting for us. Wrote up the discrepancy in the logbook and proceeded to deplane the aircraft. Cause: Mx says there was a potential fault between the landing gear handle and the sensors. That was just a guess when talking to mx on the group after landing.