For Openstack you can use the Linux Agent but for VMware you have the option of full Veeam or Agent as well.

Can we backup RED HAT Openstack virtual machines without using veeam agents?

Is there a roadmap to include an agentless backup for RED HAT Openstack in the short term?

Nothing has been announced. There’s support for Red Hat Virtualisation but not agentless Openstack. You’ll need to request this via the R&D forums at forums.veeam.com