Depending on the price you may or may not be getting 100% worm castings. The NPK according to the North Carolina Department of Agronomy shows the average NPK values at 1.1-0.34-0.40. That's really low but like other manures which are also low in NPK. The benefit to the soil is what counts most. There are also trace elements in it but "trace" is the keyword in so much as they are too small to really matter. Then again trace elements are only needed in very tiny amounts.

I agree with Karl. I always use worm castings as a soil amendment, but not the whole diet. Roses are heavy feeders, so worm castings will not satisfy them for the long haul.

I always wondered if they were really worth that much, cause if you have worms in your ground, it seems like it would be adding a couple of spoonfuls to the semi trailer load you already have in the ground.

The stuff they sell in Walmart works just fine. It is an enriched organic fertilizer, not pure worm castings.