I believe, having RCA connectors isn't the actual problem, could be 6.3 mm audio jack or XLR as well?
Recent digital reverbs are using high performance DSP chips, they can produce almost any popular audio effect by respective programming.
I presume you know what natural reverb is, a superposition of many signal echos with random delay. In the analog audio production age, it was generated by actual "reverberation rooms", with moderate quality by large steel sheets with random distributed bumps, less perfectly by multiple delay springs (as used in reverb unit of some guitar amps).
Digital delay effects are generating multiple echos in digital signal processing, superimposing them and adding an adjustable feedback for regeneration.