Yes! Frozen are just fine for jam. I cannot tell you how many times I have dug in my freezer. . .
and found hidden, frozen berry-treasure, then made jam from those delicious berries. The best were some wild grown blackberries, stream-side picked. Found those puppies and had some of the BEST jam ever!
Make sure to store them in a real freezer (like the free-standing type) for longest storage time. Don't by shy with the wrapping/packaging for freezer storate also; more is better than less.
Also, freeze in a single layer on a cookie sheet or the like so that you can pour out frozen berries easily on an as-needed basis.
If you must store them in a refrigerator freezer, plan on using them soon as the auto-semi-defrost functions will allow the berries' quality to deteriorate more quickly.