I mean, come on. We already have a lot of champs, with actual written stats, a lot of items to get on the way, just give a map of the world and make some quests and that's a full D&D adventure right there. And it's not like Riot doesn't think of making these kind of games, they already made one: Mechs VS Minions. So why not make a D&D game of LoL?
Doing it in the D&D fashion would require a crossover event of some sorts between the Dungeons and Dragons franchise and the League of Legends franchise which could involve complications between communication and legal action and some other things.
Instead, a full-on tabletop system would be the better way to go, but that involves a lot of work. A tabletop roleplaying game is a lot more complicated and involves a lot more work than Mech VS Minions.
