What door thickness can the Rollan 40 sliding door gear handle?

There is no limit to the thickness of the door, within reason.  If the door is too wide, then all you would need to do is add a wooden baton between the track and the wall, as a spacer.  The thing to be aware of is the 40kg weight limit, if the door is thicker than 55mm for example, it might be better to go for the Rollan 80, which can support up to 80kg.