They have almost 100 vessels of various capabilities. Many of the vessels named “Cape [whatever]” are ROROs though. Sealift Command also has a number of those types of vessels actively on mission.
Aren’t most of those classed as "RORO"s by MSP actually PCTCs, not CONROs?
I notice that only one of the ARC fleet ships is a CONRO, (the M/V Endurance, ex M/V Taronga):
Fleet - American Roll-On Roll-Off Carrier (arcshipping.com)
Who is ‘they’?
The Maritime Security Program (MSP) is similar.