Adding likes/dislikes, "this was helpful" and/or a public comment section to all topics

you will need a db to collect the responses.  In the past, I used lime survey with our KB web deployment.  It allowed me to embed a survey widget into the master page.  From there, you could configure the form to capture the url of the page the user entered the input on.  This was done when i was using madcap but it should be the same for using robohelp.   I eventually 86-it as the effort to maintain it (patching, security updates etc) verses the useful results I recevied was not worth it. 

As far as RoboHelp itself is concerned, you would need RoboHelp Server on every server the help is hosted on. It's not cheap.

I guess some script could work or a link to something outside your project where users could leave feedback. Alternatively you can add links for users to email you. That is covered in the RoboHelp Tour on my site.

Beyond that Frameless, not Responsive HTML5, can output to ZenDesk and other sites.

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My site www.grainge.org includes many free Authoring and RoboHelp resources that may be of help.