I stretch my binder and wrapper by casing them a bit higher than most rollers, and using a 1/4" thick, 24" x 24" piece of acrylic for my rolling surface. When it is wet, damp wrappers and binders cling to it, and you can stretch it out and it will stay. To tighten up the roll, I just pull back a bit on the cigar, against the cling of the acrylic to wrapper or binder. Don't use glass. Don't ask me why I say that.
DISCLAIMER: I roll pretty nice seegars but I am probably the slowest roller you have ever seen. My methods are not always time efficient so YMMV.