By “see wiki”, Sarel means see the RosettaScripts documentation on the Rosetta wiki. The current version of the documentation on the wiki is not available to the general public, but a copy of the version at the time of release is included with the manual (See: http://www.rosettacommons.org/manuals/archive/rosetta3.2_user_guide/RosettaScripts.html)
With regard to the AlaScan filter, there doesn’t appear to be a way to specify a specific set of residues a’la a resfile. Usually the way one will do it is by using a ReadResfile TaskOperation (or other TaskOperation which does something similar), and specifying that in the filter/mover. However, it does not appear that AlaScan is set up to take TaskOperations.