Sure. In your shell do:
export ROOTSYS=/usr/local/opt/root6
cd $ROOTSYS
ln -s share/root/icons share/root/fonts .
The first line you will need to add to your shell configuration files, or otherwise run it every time you open a new shell. Also read the Caveats at the end of brew info root6 which tells you how to run a script which sets up ROOTSYS and other variables for you.