It depends on whether you mean "role playing" as a genre of games defined by the style of mechanics, or as in the act of making in-character decisions and actions.
I was exposed to RPG like games through *very* old computer RPGS. I didn't know the term RPG at first, I just recognized the style of game of exploring dungeons, leveling up, killing monsters, and doing quests. I started at about 8 years old, and continued from there.
Some of them were old text-only completely random and luck-based simple games on the TRS-80 Color Computer. I also played the Color Computer game Dungeons of Daggorath, which had crude vector style 3D graphics for dungeons, light RPG mechanics, puzzles, etc. I also played the slightly Ultima-like game Tunnels of Doom on the TI-994A.
I didn't just like the hack and slash, kill monsters and take loot games though, I also really liked the text adventure games with stories, puzzles, exploration.
Eventually I moved onto classics like The Bards Tale, Magic Candle, and the old silver and gold box TSR D&D games like Curse of the Azure Bonds and such. Up until these computer games (and we're still in the mid to late 80's here), I had only heard the negative stories about D&D, and how it was demonic and related to witchcraft. However, I loved those games. They mixed two types of games that I enjoyed playing.
I eventually found old copies of the core AD&D books and a few others, and read through them but with nobody to play with. I found another sci-fi RPG (whose name I don't even remember) at a used book store as well, and was very interested in the genre in general. They were like the CRPGs, but more free-form, more story potential, and more social.
Eventually I made friends with some guys in High School that played, and I started playing with them. One of which I have gamed with on and off (often in D&D, but not only in D&D) ever since.
Around the same time I started playing D&D, I was also exposed to the ElfQuest RPG, and being a Chasossium game, that led me to interest in Call of Cthulhu and RuneQuest. Honestly, I didn't get to play much of those at all. Not enough interest in folks, and not enough people with the right type of style for them. They kept trying to play those games like D&D, and it ruined it.
That's pretty much how I got started.