OOC: A Medium-sized anything ought to be out of place enough on the rooftop to cause suspicion, and we can't be sure what might trigger an alarm. If it were a free-willed human, I might try the "lost dog" trick, but with a programmed guard-bot, it probably won't work. We can try it if that is the party vote, but... Animal Messenger would take too long, and requires an animal to be already present, so that won't work. Swarming locusts might work. If we want a distraction, Rikka could set up outside direct LoS (behind some of the laundry lines, for instance) and set out a locust swarm not on the target, but within view- again, might be suspicious enough to raise an alarm, but not specifically humanoid or man-made.
My votes: (1) just take this guy out, focused direct attacks from surprise (possibly using distraction to draw attention before strike. OR (2) Attempt to sneak past, one at a time, with distraction in place if he seems to have cued in (either locust cloud, Bellegon's racial darkness cloud, or thrown debris-if the target is hidden behind laundry, he might move to investigate before sounding an alarm. Anybody else have a vote or idea so we can get rolling?