First time I hit Europe, I did three weeks in an Eagle Creek backpack, which is about the size of a carry-on, with a detachable tandem bag. I've used that same bag for years. Last time I hit Europe, I took my friend's rolling bag, and it was a dream. I believe it was a 100L Nike split-compartment (like Dakine's split bags). Now, I'm looking at options of my own. I'm eyeing a few things:
Dakine split-roller 100L bags - http://www.dakine.com/p/backpacks-and-gear/luggage/travel-bags/split-roller-100l-15s
Eagle Creek has a 100L bag with no split, which I might like better. I've seen it in person and it is attractive. ORV Trunk 30 http://shop.eaglecreek.com/orvtrunk30/d/1279_c_114
For the big ducats, Eagle has this monster that is sorta tempting. The Morphus 30 is also 100L but can split into a backpack and roller combo. http://shop.eaglecreek.com/morphus-30/d/1385_cl_-1
Spend my money.
Dakine split-roller 100L bags - http://www.dakine.com/p/backpacks-and-gear/luggage/travel-bags/split-roller-100l-15s
Eagle Creek has a 100L bag with no split, which I might like better. I've seen it in person and it is attractive. ORV Trunk 30 http://shop.eaglecreek.com/orvtrunk30/d/1279_c_114
For the big ducats, Eagle has this monster that is sorta tempting. The Morphus 30 is also 100L but can split into a backpack and roller combo. http://shop.eaglecreek.com/morphus-30/d/1385_cl_-1
Spend my money.