For RFA consumer application, you can set the requestTimeout in RFA configuration file. You need to add the following config to the Connection section.
\Connections\<Connection Name>\requestTimeout = <New Value>
The default value for RFA C++/.NET is 45000 which is 45 sec. Please find more details about RFA configuration from RFA Configuration file which provided under folder "<RFA Package>/Docs"
If you need to set in in other APIs, please check the configuration in API configuration guide. The rmdstestclient is part of infra tools and I'm not sure that it can set the requestTimeout like the TREP APIs or not.
We do not have requestTimeout for provider interactive.
As far as I understand the requestTimeOut parameter is for request side/consumer, it's time the connection waits for before resending the request.
Not sure why you need requestTimeout parameter on Provider side?