After adding priming sugar and bottling a lager, does the temperature need to be raised (if so, for how long) to ensure carbonation?
Carbonate the bottles at 60-70F like ales is fine. There is so little fermentation going on you have very little "non-lager" character contributions from the yeast carbonating at that temp.
When worrying about the temperature remember that many brewers routinely ramp up the temp for a couple days to perform a diacetyl rest and that temp bump doesn't harm the beer. So carbing in the bottle at 60-70F is better than waiting 3X longer for them to carb up at 40F in your lagering space.
In my limited experience, raising the temperature of a lager when it is in the bottle is not necessary for carbonation. If the bottles are kept cold, they should still carbonate but it will happen at a much slower rate than if the temperature is raised. Depending on a number of factors, leaving the bottles in a warm environment may actually induce off flavors in your beer. I typically keep my bottles at ~60 degrees farenheit for short term storage (~3-6 months).