powershell sqlserver module discovering role members.

Trying to list members of a role in this case db_datareader by doing

dir SQLSERVER:\SQL\server\default\databases\operationsmanager\roles\db_datareader 

all it returns is extendproperties, ugh I know that I could run a sqlcmd to get the results just wanted to do it within powershell.  Is this possible with the sqlserver module for ps?

thanks