Can I list the krbtgt account that is used by each RODC in the domain?

Yes. To list the krbtgt account that is used by each RODC in the domain, type the following command at a command line, and then press ENTER:
Repadmin /showattr <WritableDcName> <distinguished name of the domain partition> /subtree /filter:”(&(objectclass=computer)(msDS-Krbtgtlink=*))” /atts:msDS-krbtgtlink