It's just as well it did have that lovely fungal growth because otherwise you might have tried to eat it and made yourself very sick.

Roasting doesn't extend the life of garlic (is food preparation, not preservation). Garlic itself is low-acid and thus higher risk as a host for some unpleasant pathogens if cooked from fresh and stored (especially if you roasted with some olive oil).

In future if you have excess roasted garlic (beyond what you'd refrigerate and use within a week) just freeze it.

Carol