You will need to add them to your own insurance. You can easily do this by downloading their Driver Qualification File (front & back of license, driving record, work history, medica certificate, etc.) and sending that PDF directly to your insurance.
There are currently hundreds of drivers active on the Relay Network. After placing an order, you will be able to see how many drivers are located in the nearby area at that time.
You as the carrier determine the worker classification as the driver is hired by you and not Relay. You can opt to hire 1099 or W2 drivers on the Relay network based on your needs and work as you see fit.