Nope. You can be off the clutch, in neutral, and just hold your foot on the brake. If you want to "roll again" (I'm assuming "forward" or "up the hill"), you clutch in, put it in first, and then gas while releasing the clutch in one smooth movement. Therefore, "riding the clutch" is not an absolute necessity when stopped on a hill.

If you want to "roll again" DOWN the hill, just take your foot off the brake...and start screaming at people to get outta the way.