The answer to your question depends on the nature of deployment that you are going to make
I'll elaborate, You can probably run everything on a single node and 8Gb of RAM and 4 Cores will be sufficient if your deployment does not require a lot of resources and if your deployment dosen't require anything to run concurrently.
If you are looking for production purposes then:
- 1 Blue Prism Application Server 2012 R2 (This is used to Orchestrate your Platform). Generally requires at least 8Gb RAM and 4 Cores, HDD used for BP is insifnificant 10Gb after OS installation should be good.
- 1 SQL Server: at least 8G RAM and HDD depends of your transacctions, logging and other configurations that you will choose when you automate.
- 1 Interactive Client, (where you will monitor your platform) 4Gb Ram 50Gb HDD
- 1 Runtime Resource :This depends on all the resources that will be used by your automation, here you have to deal with that HDD Space, and Processor Needs. You can only run 1 automation at time, so if you need to run 5 different automations (what I think that you called robots) concurrently, you need 5 runtime resources, each one must have installed the required applications.