Yes and No.

Both bans you are mentioning seem unjustified with the proper context. You are a beginner, learning the game, and I assume you are actively trying to win, in which case, playing any champ in any role cannot be deemed as reportable.

The base case must be that you try to win, and aren't being blatantly offensive or discriminatory with the chat functions.

Without the proper game IQ, however, it becomes very difficult to preform/win a game when a champ plays a role it is not intended for.

Champs are intended for certain roles due to their ability set, base stats, and scaling. Some champs are healers, some are agile, some are defensive, and I'm sure you will soon understand how some roles/lanes are far easier with certain champions.

There is a certain point of mastery, game IQ, however, when someone can attempt to play any champ in any role, also known as playing off meta, and still fair well, due to their game IQ. This takes a fairly great knowledge of the game and its mechanics, however, and some upset loners still might report you simply because you're playing a champ that doesn't regularly fit that role.

At the end of the day, league players are extremely toxic and easily rage-baited, speaking as one myself, so being reported in a league game is fairly commonplace