The problem of evil is not a problem for the atheist. It only arises when trying to reconcile a tri-omni god with suffering and evil. This is not to say that the existence of evil necessarily disproves the existence of a god, even a tri-omni one, but it does put the burden of proof on the theist.
A further word on the tri-omni God idea and all the assumptions that lay behind it. I don't begin my own search for truth with the notion of a tri-omni God, but simply with an admission of lack of knowldge. But concerning such a God one should note there are "open" theologians who cite the Bible to argue that God is not necessarily revealed as being tri-omni, but who consider that God might not know everything. If so that might make the problem of evil less of a problem.
The "free will" defense seems less convincing as a possible solution, because nature presumably got along without human "free will" for hundreds of millions of years, i.e., long before humanity showed up, God was perfecting the ways and means of nature, including carnivorism, diseases, natural disasters, along with the inevitability of death of every individual living thing. Moreover, the presumed attributes/definitions of a tri-omni God that combine "absolute freewill" with "absolute goodness" is a mind boggler. (Doesn't sound like any definition of "freewill" that human beings know about, since for us it is defined as involving a genuine choice between "good" and "evil." Neither has anyone proven that the "will" of human beings is "free" in a libertarian philosophical sense, but the tri-omni God philosophers have zipped past that unanswered question and already claim to be devising "proofs" regarding matters pertaining to things about "God's will." How imaginative of them!)