A small map in Peter Herring and Peter Rose’s book ‘Bodmin Moor’s Archaeological Heritage’ (Cornwall County Council - 2001) suggests that there are three standing stones in the area, but doesn’t give exact information on any, or exact locations - judging from the map it seems like they are 1) On the East side of Roughtor, 2) On west side of Showery Tor, and 3) on the moor to the North, near Roughtor Plantation.
As for number 3, there is a possible standing stone on Showery Tor Downs at approx SX152819 . This stone, with other stones close by, stands about 650 metres North-North-East from Showery Tor (or about 200 metres North-East from the Showery Tor Downs Cairn). There are several remains of settlements in the area.