CRJ-900 First officer reported a right engine oil level low EICAS message after takeoff. The flight crew elected to perform an air turn back and precautionary landing at departure airport.

Narrative

We had flown this plane for the two previous legs of the day without any problems. Upon pushing back from the gate and taxiing to the runway; all checklists were properly completed and the Engine Indicating and Crew Alerting System was noted without any discrepancies showing. We were cleared for takeoff; and during the climb we got a status message for right oil level low. This isn't a unique occurrence; but when we checked the level it read 15%. Throughout the day both levels had been above 80% for the previous legs; so this was concerning. We initially thought it was a reading error; until we also saw the right oil pressure gauge drop until it was amber. We immediately notified ATC that we needed to level off and return to the field. The Captain held off on requesting landing priority to ATC and they leveled us off at 16;000 feet and then began vectoring us and descending us to come back to the airfield.I continued to fly the aircraft while the Captain began running checklists and getting the airplane set up to return to the field. I noted how heavy we were when we were running the numbers and the Captain also took note of it. Once all checklists were complete and the flight deck was set up for the approach; the weight had come down but we were still going to be slightly above max landing weight. I asked the Captain if we should continue to get vectors and burn the extra fuel or if we should land. The Captain made the Pilot in Command decision to land the aircraft slightly overweight as he didn't want to risk the oil pressure dropping further and potentially losing an engine; because that would cause even more issues and could potentially risk the safety of the passengers. We were cleared for the approach and landed without incident smoothly at 75400 lbs.; roughly 300 lbs. overweight since the aircraft was a CRJ-900. Once we had taxied off the runway; the right oil pressure warning message came on and the Captain shut down the engine. We taxied and parked at the gate without further incident and maintenance met us at the gate. We notified maintenance; dispatch; and the occurrence report of the overweight landing accordingly. In this situation; although we hadn't [requested priority landing]; it could have easily progressed to that point. So the options we faced were to either land slightly overweight but get the plane on the ground as soon as safely possible; or don't land overweight; continue to get vectors until we burn the fuel; but risk the oil pressure dropping to an [priority] situation; losing an engine; and risking the safety of the passengers. Both situations have their pros and cons; but thinking of passenger safety; and how close we were to landing at the correct weight; the Captain chose the Pilot in Command decision to return to the field and land slightly overweight.