a1g 1-4 ( 2 ) a2g 1 ( 2 )
b2g 1 ( 1 ) b3g 1 ( 1 )
$rohf 1 a -a a=0 b=0 h -h a=1 b=2 a -h a=1 b=2
$roothaan a = 3/4 b = 3/2
For further information on ROHF calculations (e.g. with more than one open shell), see the sample input in Section 15.6 and the tables of Roothaan parameters in Section 6.3.
Note that this keyword toggles the ROHF mode also for more than one open shell. If it is not given, the open-shell electrons are simply ignored.