Roamers are man made fighting machines created for the purpose of war. They were made to cut down on human casualties. After the brutal murder of the team devoted to working on the Roamers, they were decommissioned and put into storage.
The Apex's were the first 10 Roamers ever made. There are ONLY 10 in total.
After the Apex's were put into storage a group of thieves, with the intent of using the Apex's to gain power and fortune, broke into the storage and stole the Apex's. The group ended up being torn to shreds by Apex-001 Morgan and the Apex's were free to roam the world. After a demon by the name of Neptune befriended a few of the Apex's she managed to use there coding and model blueprints to creature more, less dangerous, Roamers. These Roamers were known as the Non-Apex's. A Non-Apex is any man made Roamer after the decommissioning of the Apex's.
After the arrival of Non-Apex Roamers, Offspring's soon followed. An Offspring Roamer is the product of two Roamers procreating and producing young. Any Roamers can produce offspring's regardless of gender. Offspring Roamers are living creatures and are in no way mechanical.