bbPress Protected Forums adds a metabox, shown while editing a forum, that allows you to disable new topic creation for determined user roles.
The plugin is perfect for those situations that you may want your users to see the list of topics of a forum but don’t want them to create new topics.

bbPress 2.x

Plugin fully compatible with bbPress 2.x

Languages

bbPress Protected Forums is currently in:

English
Spanish

The plugin comes with .po files. Feel free to translate it to your language!

Official site

For more information about this plugin you can check the official site.