It can be wise to make a disinction beween the HOPEX web application server (web server, application server) and the database server. Database can be managed by DBA and HOPEX application server by project. Note that if a database server already exists, it could probably host HOPEX data.
If you have limited resources (one server), you can use one for all roles (web server, application server, database server).
Note that running the database server on the same machine will increase the CPU/Ram requirements.