The recipe calculator I use (at BMW) gives about 25 pts per pound per gallon for roasted barley, compared to 28 for 2-row. So yes, sugars are available. Maybe what he meant was that the enzymes for self-conversion are destroyed. This is not a problem, since your base grain provides plenty of enzymes to convert the small amount of roasted grains.
In any event, the vast majority of the fermentables are provided by the base grain anyway, so it's not a significant point to argue. Unless, of course, you and your brother typically go to the mat over small details.