Welcome to Flyertalk, Lulrus.

The Ziploc bag requirement you refer to applies to liquids/gels/aerosols in carryon luggage, not checked bags. You do not need to remove the product(s) from the box(es) unless you want to for space reasons.

As for the quantity you cite, it's really none of the TSA's concern that you're checking a year's supply in one bag but my instinct would be to minimize the appearance of excess. If possible, buy several of the 90-day supply boxes rather than 10 of the 30-day supply boxes. I would maybe put the boxed product into gallon size Ziplocs if accidental spillage is a concern but otherwise wouldn't bother.

Are these really aerosols like canned hairspray? I was under the impression Rogaine is a dispensed as a foam from low pressure plastic containers?