Microsoft supports a limited set of role collocation. The official documentation can be found on Technet.
On a Front End server, the Mediation and/or the A/V conference server can be collocated in a Production Environment. You can collocate the Archiving and/or the Monitoring role on the database server. The Edge server and the Director cannot be collocated with any other role. The File Share can be collocated with any database server, the Monitoring server or the Archiving server. The File Share cannot be collocated with the Front End Server.
The collocation of the Reverse Proxy or Exchange UM servers with any Lync role is not support.
|Role||Supported role collocation|
|Front End Server||Database (SQL Server Express) for Standard Edition|
A/V Conferencing Service
|Database Server (Full SQL)||Monitoring Role|