Rugido de la multitud

Spells and abilities that prevent damage or regenerate the targeted creature must be cast or activated before the creature type is chosen.

You choose a target for this spell as you cast it, but you don't choose a creature type until the spell resolves.

Note that this spell counts the number of permanents you control of the chosen type, not just the number of creatures you control. It will also take your kindred permanents of the chosen type into account.