Is it possible to select a single object from a group created like this?
var r = new fabric.Rect(...);
var l = new fabric.Line(...);
var roadGroup = new fabric.Group([r,l],{ ... });
So I want to have a group, but select objects l or r separately.
The simple answer is yes, but you should make sure you take into account the purpose of a group.
To get a handle on an object that is wrapped in a group you can do something like this:
var r = roadGroup._objects[0];
var l = roadGroup._objects[1];
To select a child of a group try something like this:
fabricCanvas.setActiveObject(roadGroup._objects[0]);
soapbox:
The purpose of creating a group is to treat several objects as if they were a single one. The purpose of selecting an object is to allow user interactions with an object. If you want your user to interact with a portion of a group, you might want to consider not grouping them in the first place, or else un-grouping them prior to selecting the child object.
/soapbox