Roselady Barossa VS ChimeraDragon Hydrus

I'm confused, my opponent has Roselady Barossa (3-64), effect says all my yellow spells are free during my battle phase, I have ChimeraDragon Hydrus (4-74), which says the opponent must pay actual cost of spell cards. What will happen if my opponent attacks then plays, lets sayTime Reap (2-107) will he pay the actual cost (Hydrus's effect) or will the spell be for free (Roselady's ability)?

You would have to pay the cost since Hydra is a permanent effect and that proceeds over any other triggered effects like barossa since she is just during your battle phase.