I'm not a expert on imagex nor provisioning. I've only used imagex doing a manual PXE Boot..
First after creating the partitions you have to format them because imagex is file based.
Second Imagex only captures 1 partition so as far as I know you would have to have 2 imagex images, 1 with the os and 1 with the reserved. Set up the template to install 1 image to its formatted partition then install the 2nd image to its formatted partition.
Also after imaging you have to run bcdedit to fix the boot sector.