Hi,
Roboform and others passwords manager such as Lastpass were already available when we decided to launch. I would say that the ambition of Dashlane is different. Dashlane is not about just about password but we try to offer a new experience on the web where there is no need to switch between keyboard and mouse all the time. We have worked a lot on the user experience and everything has been designed to be simple and convenient.
Dashlane is also very different when it comes to online shopping. not only does Dashlane make check-out much simpler but in addition Dashlane gives a global history of every purchase in the app with many details. We really want to be the simplest solution to manage personal data. Feel free to have a look to our demo videos if you want more information: https://www.dashlane.com/en/tour#clicktopay