How do I pass credential file to mount.cifs?

Syntax of mount.cifs:

mount.cifs {service} {mount-point} [-o options] 

You need to pass the options after the "-o". For example, with your given options, your command should be:

mount.cifs //myserverhere.com/cifs_share /mnt/cifs_share \
    -o user,uid=65001,rw,workgroup=DEV,credentials=/root/.cifs

(I didn't test the options you gave.)