The answer to almost everything in poker is, it depends. But in your case, we have an affirmative answer.
It's impossible to lose money in freerolls (except when the re-entry fee is charged)... So, in theory, you can only be EV+ by playing freerolls! Haha
I answered somewhat jokingly, but with a grain of truth! Haha
In general, yes!
You need to dedicate yourself, at least a little, to understanding the game. Set your goals.
Ideally, you should build a decent bankroll from freerolls so that you can then think about being profitable.
Cardschat alone offers almost 100 freerolls per month, and of course, depending on how much extra income you need, you can withdraw something just from those (obviously by dedicating yourself). Besides the thousands of others that exist out there, not with the same structure and probably with gigantic fields, but they can still help increase your bankroll. It will also depend on your availability for the game.
There are several factors, but since it's impossible to be completely profitable playing frerolls, then we're all profitable! lol