I'm trying buttercream piping samples this week...

I have made a few roses, but they are quite "flat" or low-profiled, and I"m wondering how to attach each petal to get a deeper rose? is it just a matter of using a bigger petal tip?

Heheheh... Looks like it's "Annoying BC Roses" night. Hope you get your issue resolved

When you pipe them are you starting below where the last row was? Or are you piping them all at the same point? You may try moving your petal tip lower for each row.

When you arrange them in groups on the cake, you can always add a small pile of buttercream under them to give them some height.