SR22 pilot reported engine roughness during cruise. Pilot attempted troubleshooting; returned to departure airport and landed safely.

Narrative

We departed ZZZ on an IFR flight plan at night and leveled at 12;000 feet in accordance with our clearances. Upon leveling at our cruise altitude of 12;000 feet; the routine adjustment to the engine was made to achieve LOP cruise. After approximately one minute of flight at cruise power settings; I experienced what felt like an engine 'stumble' or 'miss' that was inconsistent. I verified that the fuel boost pump was operating normally. I switched tanks to eliminated the possibility of water in the tank that may have been causing incomplete combustion. Neither of these changes impacted the engine roughness. I adjusted the mixture slightly richer and slightly leaner of the median setting (that the POH specifies) to determine if that would have a beneficial effect and it did not. The engine 'stumble' became increasingly worse and the CHT1 temperature climbed from a normal ~350F degrees to +/- 428F; causing a caution indication; and exceeding the 425F maximum sustained cylinder temperature. I immediately pulled power back to 50% and moved the mixture full rich to cool the cylinder as much as possible and relieve stress on the engine. I contacted ATC and requested to divert back to ZZZ due to the unresolvable engine problem that I feared might become worse. They cleared me direct and I made an immediate right turn direct ZZZ while maintaining as much altitude as possible. I notified ATC that I was unable to hold altitude; however we were able to maintain a descent rate that was under 500 FPM with minimum load on the engine. ATC offered a lower altitude clearance and advised they were [granting us priority handling]. I lowered the power setting to 30%; maintained full rich mixture; fuel boost pump on; and trimmed for slower flight that would maintain longer glide distance to the next available runway in case the engine were to quit entirely. The route back to ZZZ kept me in a position to land at ZZZ1 if that became required. I was able to maintain minimum power at 30% and was handed off to ZZZ Approach; who cleared me for the visual into ZZZ. When landing was assured with the minimal power setting; I added 50% flaps and successfully landed at ZZZ without any damage or injuries. I was able to taxi the aircraft back to the hangar and shut down with no further incidence. I called ZZZ TRACON on the phone number and cancelled IFR; thanked them for their support; and answered the questions they had about the aircraft mechanical issue that occurred. I contacted a Cirrus-authorized AOG mechanic to schedule assessment and required repairs.