ROOT must have certain environment variables defined. To define these variables invoke in your shell the appropriate file:
For Bourne type shells (sh, ksh, bash, zsh...)
$ . /home1/oua4/d0depot/local/etc/set_root.sh
For C type shells (csh, tcsh...)
% source /home1/oua4/d0depot/local/etc/set_root.csh
This defines the environmental variables ROOTSYS, LD_LIBRARY_PATH, and adds the ROOT binary directory to your PATH.