You should get the sample test data from Open Channel Foundation when you get ROI_pac (you can also get it separately there). This allows testing of the operation of your installation. You can run the test automatically with the contrib/multitest.sh script, or do the two "make_raw" runs and "process_2pass" steps by hand. The ROI_pac internals document goes through the steps showing the output.
A common place for ROI_pac to fail is when it is matching the two SLC images to determine the necessary coregistration paramaters, using the ampcor program. It first runs a "gross" matching at a smaller number of locations with a large search distance. Then those offsets are analyzed with the fitoff program to estimate an affine transformation between the slave and master SLCs. The output is in the file "fitoff_ampcor_gross.out" which should look like this for the test data (e.g., TEST_DIR/int_930110_950523/fitoff_ampcor_gross.out ):
<< Fitoff Program >> Number of points remaining = 320 RMS in X = 0.19749243553571993 RMS in Y = 0.35261127314144114 Matrix Analysis Affine Matrix 1.0000245614 0.0000196524 -0.0002626832 0.9999805914 Translation Vector -10.658 22.246 Rotation Matrix 0.9999999655 0.0002626767 -0.0002626767 0.9999999655 Rotation Angle (deg) = -1.50502674772483684E-002 Axis Scale Factors 1.0000246 0.9999806 Skew Term -0.0002430