Hi, everyone. I'm fairly new to decorating. I've followed wilton and cake boss' directions on making buttercream roses but they always come out with jagged edges. What am I doing wrong?

A couple possibilities   Nothing!  I can’t see your picture but I think ragged edges  makes them more realistic :)    Your icing probably needs a bit more fat/shortening to make it smoother   Next many people say to open the narrow end of the tip w/a butter knife  I never did in over 30 yrs of decorating     Also Try squeezing harder &/or turn the nail faster as you pipe    These are all things that can help you make beautiful roses