I have some Alfalfa Pellets that I have had for two years. The mice have been in them and I wondered if it would be safe to use or should I get a new bag? Next time I will store them in a plastic container.

I doubt the roses would know the difference. Alfalfa pellets/meal/hay are put in a bucket or larger container, filled with water and let brew for about 10 days. Then it's watered into the soil around the roses. Alfalf is only good for the roses when it's decomposed. So if it's only for the roses and the soil, your old alfalfa is perfect.

You don't have to "brew" it, you can use it straight on the ground around the roses. It will be OK to use or to compost, if you make your own compost.

Some people make a tea with Alfalfa and pour the tea on the plants and soil and throw the material used to make the tea away when that too could be put on the soil. Almost any kind of organic matter is always good to add to soil, and those you have would be better added to soil then the alternative, tossing them into the trash.