Riddles? Oh no. Olly was not particularly good at riddles. He could solve most problems if there was a clear answer and a fairly simple way to get there. But riddles were not very straighforward, that was the whole point of them. You had to think outside the box. Olly was not necessarily good at that sort of thinking. Luckily he did not have to solve it on his own. He was in a class full of people who were all (audibly) solving the very same riddle and then doing as it said. That made things a lot simpler for him.

Comes from the ground and sky. What did that mean? Something roses needed to survive. He thought about that, trying to solve it on his own first. That wasn't too difficult. Olly brightened. He could practically feel the light bulb above his head. Water! That's what it was. Of course. Rain came from the sky, and there were lakes and ponds and whatever in the ground. And flowers needed it to survive of course. Olly quickly took out his wand to help give the roses some water.

"Aguamenti."