This documentation snippet tells that the aptitute module allows installation from .deb file, like this:
# Install a .deb package
- apt: deb=/tmp/mypackage.deb
I get the following message when I run it. 
- name: install riak
  apt: deb=/data/riak/riak.deb update_cache=no
produces this output:
TASK: [riak | install riak] *************************************************** 
failed: [riak-server-1] => {"failed": true}
msg: unsupported parameter for module: deb