Sign API - multiple signers with specific roles

I am building an Adobe-based POC for a company that performs very significant amounts of document-signature processing.  I'm also new to Adobe Sign so my use case may be supported and I'm just missing how to do it.

I want to create signable documents where each recipient equates to a specific role and each recipient sees only their initial/signature locations.  For example, in a real estate transaction the roles might be "buyer, seller, title agent, escrow agent,... ". I want each of these to receive a document with ONLY THEIR initials and signature locations rendered.  Something like..

1. The buyer should receive a signing document with initials requested on line 50 and line 100
2. The seller should receive a signing document with initials requested on line 75 and 125
3. The escrow agent should receive a signing document with signature requested on line 200. 

I am using the programmatic APIs for both document merge and document signing - all user interaction is via a custom React front-end with the custom middle tier is leveraging the Sign REST API (e.g.https://api.na3.adobesign.com:443/api/rest/v6/agreements). Thus, the transient document only has role-based signature blocks and the signing JSON supplies the actual email values.

WHAT I TRIED...

I would think this would be supported by having the role identified in the signing tag:

{{*buyer_es_:buyer:initials}}

and then mapping in the JSON that indicates the relationship

"memberInfos": [

        {

          "id": "buyer",

          "email": "fred@example.com"

        },

However, this approach still renders/requests all signature blocks for all of the roles - it does not render only the specific blocks required of this signer. 

Is there a way to map these so that we can be precise about which role/recipient is prompted for their inits/signature?