The speculation behind this signing has a lot of logic behind it, that's why it's rated as an H4:
1) Gary Roberts won his one and only Stanley Cup with the Calgary Flames in the 88-89 season. That's going to mean something
2) He'll be returning back to Canada and knows the fans are way better than they are in America
3) http://thepensblog.blogspot.com/2007/10/wwgrd-wristbands-vote-vote-vote.html These wristbands would go crazy in Calgary. I'd probably by 10 000 of them. Everyone in the city would own it. He'd be more of a cult icon than Sean Bean.
4) Darryl Sutter is one of the worst GMs at signing free agents. Recent aquisitions since the lockout: Tony Amonte, Darren McCarty, Owen Nolan, Adrian Aucoin ... there are more but I'm too lazy to research. What's the similarity between the four free agents he signed? They are all 35+ years old. Gary Roberts is ripe at 42, this will be Sutter's oldest free agent signing yet! He must be so excited.
5) Picture 20 000 fans at the Saddledome during a playoff game chanting "GARY GARY GARY GARY!!!" As he challenges the all the Red Wings on the ice to a fight. That's almost Zach Stortini style.