Now that the CA is installed, you can go back in and add the remaining roles:
Step 1. From Server Manager, select Add Role Services for the CA.
Step 2. Click Next.
Step 3. Select Network Device Enrollment Service, and then select Certificate Enrollment Web Service.
Step 4. Click Next.
Step 5. Specify the service account user created previously.
Step 6. Click Next.
Step 7. Fill in the Registration Authority ...