Conan O'Brien Speaks Out About His Friend Rob Reiner's Death

Conan O'Brien is finally ready to discuss Rob and Michele Reiner's deaths ... opening up about the tragedy in a new interview released Friday.

The comedian talked about his relationship with the late director and his wife in a piece published by The New Yorker ... revealing he and his wife became increasingly close to the Reiners over time.

O'Brien says the two were lovely people ... and, finding out the Reiners were dead just hours after he bid them good night left him in shock for a long time afterward.

Conan went on to laud Reiner for his professional accomplishments ... especially his unprecedented run of successful films he helmed during the 1980s and '90s.

Reiner could've just made "Spinal Tap" and been considered a legend, Conan says ... the fact that he made anything else so remarkable was just icing on the cake.

We broke the story ... Rob, Michele and their son Nick Reiner -- who was arrested for their murders -- attended a Christmas party at Conan's residence hours before the two were brutally stabbed to death, and Rob and Nick had gotten into a very loud argument at the party.

Nick is set to finally be arraigned Monday ... though, as we broke down in our documentary "TMZ Investigates: The Reiner Murders: What Really Happened" -- available to stream on Hulu -- a change in Nick's schizoaffective disorder medication may have contributed to the outburst and his parents' deaths.