Do fatty acids and glycerol both use simple diffusion to be transported across the plasma membrane?

no

less sure about glycerol but FFAs have various transporter proteins for the cell's lipid bilayer as well as for the mitochondrial membranes

This post was edited by cloudkicker on Jan 28 2015 07:52am

Yes and no
Glycerol does freely diffuse
FFAs do freely diffuse as well. Though they also utilize some facilitated diffusion through a channel or adaptor protein too.. Though it still doesn't require ATP