Are the offspring of parents who are both homozygous dominant for normal red blood cells in danger of getting sickle-cell anemia?

No, 0% chance

Explanation:

none of the parents are carriers of this disease, and are homozygous dominant to the normal red blood cells, so they will not inherit this disease

If both parents do not have sickle-cell anemia, than the possibility is low.

Explanation:

If both parents have the sickle-cell trait, their offspring has a 25 percent chance of getting sickle cell anemia and a 50 percent risk of them having sickle cell trait. Meanwhile, there is also a 25 percent chance of the child not getting it at all.

If one parent has sickle cell anemia and the other has sickle cell trait, then their offspring with have a 50 percent chance of getting sickle cell anemia and a 50 percent chance of getting a sickle cell trait.

When both parents have sickle cell anemia, their child will definitely have it.