My decommissioning steps are detailed below:
1. In the OCS 2007 R2 Administrative Console, expand Standard Edition Servers, expand your servers computer name and then right click the "Users" container and click "Delete Users". Follow the presented wizard to remove all OCS attributes from your SIP enabled user accounts.
Note: This does not delete your Active Directory user accounts, it simply SIP disables the users.
2. Right click your servers computer name and select "Deactivate", then proceed to deactivate each role in the following order. Performing these steps in the incorrect order will impact the uninstallation of the product.
Response Group Service
Outside Voice Control
Conferencing Announcement Service
Conferencing Attendant
Application Host
Application Sharing Server
A/V Conferencing Server
Web Conferencing Server
Web Components Server
Front End Server - If deactivation fails, run this again but check the force option.
3. Once the deactivation is complete, go to the control panel of your server and select either Add/Remove Programs or Programs & Features depending on your operating system version. Proceed and remove the following services in the below order.
Application Host
Application Sharing Server
Audio/Video Conferencing Server
Conferencing Announcement Service
Conferencing Attendant
Outside Voice Control
Response Group Service
Web Conferencing Server
Standard Edition Server (Front-End)
Managed API 2.0 Core 64-bit
Managed API 2.0 Speech x64
Managed API 2.0 Windows Workflow Activities Server Speech Language Pack
OCS 2007 R2 Administrative Tools
Web Components Server
Core Components
4. Demote your server from the domain and proceed to delete it's Active Directory computer account and its associated DNS A and SRV records.
That's it, you have successfully removed Office Communications Server 2007 R2 from your environment.