I want to start this out with a disclaimer: I am not professionally trained in the science of handwriting analysis. Neither are the "professional" authentication experts at third party authentication companies. What they do is provide a service where collectors pay them for their opinion on whether something is likely authentic or not. The problem with that is they aren't always right. There have been numerous articles written on the subject of incorrectly authenticated memorabilia dating back as far as 20+ years ago.
While I'm not an "expert" on the authenticity of signatures, I have spent numerous hours pouring over authentic copies of autographed Scott Rolen cards, pictures, baseballs, bats, and other memorabilia. I have even outlined the evolution of Scott's signature over the course of his career on this site. I've also had pieces signed by Scott in person and witnessed the flow of his autograph.
This 8x10 is currently for sale on eBay and it has been authenticated by a third party authentication service. But the problem is, in my opinion, this is not a real Scott Rolen autograph. I don't think the person in charge of authenticating this piece spent any time looking over the nuances of the signature at all. Allow me to elaborate on my observations:
Scott doesn't stack his signature with his first name over his last name. He doesn't do that on baseballs, baseball cards, bats, or photographs. Even when space is constrained, Scott doesn't stack his signature. Take a look at the Evolution of an Autograph; specifically the 2002 autograph. Scott signed this 2002 Topps 206 card and that card is the size of a tobacco card. The card that was signed is quite narrow and would have been as good a time as any to stack a signature on a card, but you see that Scott didn't do that.
Because of the way he signs his name, the crossing of the 't' in 'Scott' flows into the 'R' of 'Rolen'. It is one continuous fluid motion. The other thing to note here is the 'S' in 'Scott'. The top of the 'S' abruptly changes direction from the top of the letter to the bottom of the letter. I'm not sure when this piece was allegedly autographed by Scott, but in his early signature (1995-1996) his 'S' did abruptly change direction, but there was no loop at the bottom of the 'S' - it looked more like a lightening bolt. The loop at the bottom of the 'S' began in early 1997 and at the same time, the top of the 'S' was rounded.
This picture had to have been taken during the 1997 season. The patch on Scott's right sleeve is the Jackie Robinson 50th Anniversary 'Breaking Barriers' patch. That small detail only adds to the fact that the 'S' in Scott's first name couldn't have been signed when he was using the lightening bolt style 'S'.
I say all of that to say this; know your subject. When purchasing an autographed piece, don't put too much weight into what someone else's opinion on the piece is especially when they are being paid to authenticate something. Do your own research and get familiar with the autograph you're looking to buy. Obviously everyone is free to collect whatever they would like - that's the beauty of the hobby. I will personally never pay a premium for anything that is "authenticated" by any third party authentication service.