I can play 2/3 champ from every category (all mage and support also)
But knowing to play a lot of champ and trying to carry randoms is not like helping you a lot in soloQ
To play solo, you may better pick carry or split pusher role. Despite that, you may need to adjust the pick/counter pick. So, learn to play 2 or more heroes of different roles, being a one-trick hero autolocker is bad though. Many people pay less attention on pushing and objectives, though it's more important to win the game, but as a solo player you'd better to do such that.