vRA does not currently manage an AWS image primary volume, It will build the ec2 instance with what ever size disk the image was built with. The easiest way is to create your AMI's with an 80GB disk, this means all machine spun off will have that size. Additional disks are fine.
I am also interested in such a feature. It might not be a big deal since it is also possible from the AWS console during instance launch wizard:
So, might it be possible to add this, i.e. with a new custom property?
In general, I am wondering why this isn't possible yet since there are already related custom properties that allow to set the Volume Type and the IOPS.
Thanks and Best Regards,