Pity you left rough side out if you knew you were going to paint it. I've been painting osb for 20 years and latex works and will last years. Depends if it is exposed to sun or not. Lately I have found that the Dulux brand of Melamine paint (Home Depot) works the best. You can have it tinted whatever color you like and it gives a smooth finish that handles weather well.
DON'T use a plastic paint. It will start peeling off after 1st year.
There shouldn't be any difference with the rough side out. Although the platen side might give you a better finished look with no nail lines and a smooth finish. If your panel is 100 percent MDI it will probably stand up to the weather better as well.
Hands down Behr premium plus ultra paint and primer, or the Behr marquee are the best paints. Being a contractor and having a great deal of experience with interior and exterior paints I have never seen anything cover or hold up as good. Built my house 6 years ago and used smart panel vertical siding which is an OSB product and painted it with Behr paint (lifetime warranty) , It still looks like it was painted yesterday with absolutely no fading, or chalking.
Painting OSB panels
Linear Mode
