Deploying a resource adapter archive in the deployments directory should work just as with any other archive deployment type (WAR, EAR ...). You will need to of course fully specify the deployment properties for your resource adapter in either the ra.xml or ironjacamar.xml files in the META-INF directory of your resource archive. Alternatively you can use the AS7 Admin GUI to do the deployment under the 'Managed Deployments' tab.
HTH'