I've recently built up a specialized awol with Salsa lowrider racks. I'm using it largely for commuting so I don't need a load of room, just enough for my laptop, lunch and extra clothes. I've been looking at the Ortlieb HR Front-Roller Classics and they look like they would serve my purpose well. The only issue is that my macbook pro is slightly to big for the given dimensions (Panniers: 30 cm x 25 cm x 14 cm, Laptop w/ case: 38.1 cm x 27.4cm x 3 cm ). I know sometimes you can "overstuff" rolltop panniers to fit more in. Could I pull this off with the Ortliebs. If not do you have any other suggestions for waterproof/water-resitant, relatively affordable panniers that would work in my case? Thanks!
I tried a number of front loading setups for an AWOL with a 15 inch laptop (same model). I could only ever get the laptop to fit in front Ortlieb rollers only with minimal protection on the laptop (e.g., wrapped in a towel). Even then I couldn't roll the top sufficiently to seal for anything other than a very light misting of rain.
I ended up stabilizing on Ortlieb rear rollers and using either a Tubus Duo lowrider rack (as the lower brace is low enough to support a large pannier [unlike the tara], but requires inner and outer mid-leg attachment points [which the AWOL has]) or a Specialized Pizza rack with the same panniers (pictured below). Most other front racks do not extend down enough to support large ortlieb panniers. You also might be able to mount the computer on the top of a Pizza rack, however I wasn't able to get Ortlieb front rollers to fit well on the pizza rack (the lower support bar is too low for the lower pannier hooks).
Another option is keeping your setup and mounting the computer on the rear of the bike. I found the AWOL quite handled well putting the 15 inch laptop in a rear pannier while keeping food and cloths up front (this setup actually handled better than front loading everything). You could keep your current front setup and look at running a single rear pannier to house the computer. (Probably your best option, but unfortunately requires buying more stuff.)
Some final notes. The Salsa low riders put the panniers a fair bit forward of the front axle which will make the steering feel heavier initially, but will interact with the wheel flop to turn the bike in harder when leaned over (in my estimation). Also avoid running all the weight on the rear of the AWOL, as this makes it handle like an unhinged squirrel mad for nuts.
I suggest you find a bike shop that stocks it and take the laptop. I work round the corner from a big branch of a chain. If it's on their website (and I'm sure it will be) they can get it in next day for you to try. In my case it's near enough my cheapest option as well taking into account delivery charges elsewhere.