Age 10 or 11 for my own CRPG- Gateway to Apshai. Then probably Ultima 3 after that. I had played Ultima, Wizardy and Temple of Apshai at friends' houses before that. For RPG it is likely 7 or 8, playing basic D&D with my older brother and friends.
I was part of the D&D craze back when it hit big in the early 1980s. I must have been around 13 when I first got introduced to it by my next door neighbor, he was 20-something and he had a bunch of us neighborhood kids start to come over for long D&D sessions. It was a lot of fun. And then I also would play at lunch time in middle school too.
If you mean computer role playing games, I did play some of that text game Zork, but I came late to computer rpgs you might say, I missed most of the 1990s era, my first real one that I played was Baldur's Gate. I was absolutely amazed at that game at the time, and it hooked me real good on the crpgs.
My first RPG was RuneQuest which I played at the age of about 10. The second one was Cyberpunk 2020 which we played at the verge of teen age. I was so proud of playing PnP RPGs instead of playing with Legos that time In retrospective, they both were similar kind of child's play and I should not have felt ashamed to play with Legos. I liked RPGs so much that volunteered in a local RPG store for work practice when I was at the 6th class. I still remember how the workers would LARP in the store when there were no customers. One, who had a toy sword, would be an elf and fight against a "dwarf" with a hammer. The dwarf lost because the elf summoned a river in between them and dwarfs could not swim. Even though these guys were >40 and I was 12, I think I was the least child in that shop
My first computer RPG was Ultima 5, which I played around the same time than RuneQuest. I could not understand anything about that game since I could not read English. All I remember how scary the blue robed ghosts were and how cool it was to get magical throwing axes for the entire party. Baldur's Gate came out when I was 15 and blew my mind away. It was so fancy and modern! That's still one of the few games I have finished multiple times.
Regrettably, I am too busy these days to play PnP or cRPGs. Also, I have partly lost interest for them but am sure that it will come back one day. It would be fun to play, for example, BG3 with a group of people when it comes out.