Reading the dawn of Yangchen. I can't be the only person that finds it incredibly funny that Roku seems to be only avatar within several generations to have a traditional avatar journey resulting in him being told at age 16 and only mastering all four elements in his mid 20's? Yangchen found out herself when she was like 10 ish bc she was plagued by nightmares of past avatars, and was already an established avatar when we meet her at age 16-17 in the first novel. Kyoshi only found out when she was 16 bc the earth kingdom method of identifying the avatar doesn't work when the avatar's an orphan and they thought it was someone else first, but she mastered all four elements in less than two years. Aang was told at age 12 because of the war looming around the corner, and had to master all elements within less than year out of pure necessity (i say less than a year bc Aang was told abt the comet during the winter solstice and the comet appears at the end of summer). Korra discovered she was the avatar at the ripe old age of four or five and managed to bend three out of four elements by that age, and mastered all four at age 16.
To be fair to Roku, we're not really told how old Kuruk is by the time he masters all four elements. I'm pretty sure he was told at age 16 as well but I'm assuming he finished his journey earlier seeing as he died at age 33. Kuruk's story was also quite a bit more exciting (and dark) because he fought dark spirits on the regular. Roku was just kinda there. All he did was be bisexual and fail to prevent his bestie from colonizing the world.
All of this to say, out of all avatars in the immediate surrounding cycle, Roku once again comes out looking a bit like a chump and I'm loving the consistency lmao