ROP

A ROP is basically a smaller APE (additional polling engine) it has the same requirements and yes it supports the same modules. It is limited by licensing compared to a full APE. Installation is similar to an APE.

Supported Modules by a ROP:

• IPAM
• NCM
• NPM
• NTA
• SAM
• SRM
• UDT
• VNQM

More information:

Scalability Engine Guidelines for SolarWinds products

it should also communicate with the Orion database or it need a dedicated SQL server located on the remote site ?

It is just like an additional polling engine - it will communicate with the orion database. The additional polling engine requirements for connectivity and network latency still apply. 

From the scalability engine guidelines:

Requirements for APEs

The latency (RTT) between each additional polling engine and the database server should be below 200 ms. Degradation may begin around 100 ms, depending on your utilization. Ping the Orion SQL Server to find the current latency. A reliable static connection between the server and the regions.

It is just like an additional polling engine - it will communicate with the orion database. The additional polling engine requirements for connectivity and network latency still apply. 

From the scalability engine guidelines:

Requirements for APEs

The latency (RTT) between each additional polling engine and the database server should be below 200 ms. Degradation may begin around 100 ms, depending on your utilization. Ping the Orion SQL Server to find the current latency. A reliable static connection between the server and the regions.