Unless you get bugs or varmints in your scratch, I wouldn't worry about that going bad--dried, whole grain like that stays good for years, though maybe you don't want to let it go that long, and there's no reason you can't feed your rooster laying feed--especially if you are supplementing with lots of treats.
Another option, if you have a little extra freezer space, would be to freeze at least part of your feed in gallon sized zip-lock bags, then you'd be able to use more from each bag. You might also see if you can find someone else in your area who has chickens that will let you split a part of one of their bags. If I knew someone with only a few birds, I'd be happy to sell them ten pounds of feed from one of my bags.