vRA will allow you to create a reservation without a network profile. The machine will provision on one of the network paths available on the reservation just without any IP information. You will receive the properties VirtualMachine.Network0.Name (this is the network path) and VirtualMachine.Network0.MacAddress that can be used in your workflow to get the correct IPs and then set the properties for the allocated IP.
A far as I know, vRA don't have any way to talk with an external IPAM.
What I would do is to stop using Network Profiles, install vCO customization and work with the "WFStubBuildingMachine" to call the IPAM system and manually set all the custom properties on the VM, including:
You can set the VirtualMachine.NetworkN.Name to select the proper network on the blueprint.
Actually, we can talk to IPAM. The Hands on Lab 1632 shows off the integration with Infoblox. There isn't an OOTB plugin for solarwinds but you could integrate it with Orchestrator.
I don't know if you got the answer you were looking for. This isn't anything someone didn't already say.
If you want to integrate with your own IPAM just don't use vRA network profiles at all. Extend vRA into vRO and use vRO to call your IPAM tool to retrieve your IP assignment. in vRO use the vCAC workflow "Update property on vCAC VM" to set the networking properties, suggested by bdamin above, of the vRA VM .
In the case of Infoblox we use a pure vRO version (custom) of the plugin. Try to stay away from modifying the vRA workflow stubs it gets nasty quick. vRO is where you want to be.
Just to update this thread.
Solarwinds has now developed a vRO plugin for Solarwinds that can be used with vRA as an external IPAM. IPAM integration with VMware vRealize Automation (vRA)/Orchestrator(vRO) - SolarWinds Worldwide, LLC. Help and Support
I've not yet used it, but some customers are looking on it.