rgn87,
There is some variability between flocks and individual runners - here is what we have going.
I have ten runner females, black and chocolate. Their "summer cottage" is a 4'x8', 4' tall double-walled insulated plywood box with a Dutch door for me, and a sliding door for them. The slider goes to a porch (the veranda, I call it), that is covered on all sides with half inch hardware cloth. The veranda is also 4'x8', so that's the room they have at night when nighttime temperatures are above 40F (That is its own story).
In the colder times, I have them in a more or less 60 sf pen in the walkout basement, where it is in the mid 40s F. During the day when the weather is decent enough (20s or above if sunny, 30s or above if not), they are outside in the garden (when I can watch them), which is about 500 or 600 sf, or in their 10'x16' completely enclosed, sides, top, bottom, day pen.
They bathe in a 2'x3' 10" deep concrete mixing pan.
Based on my ducks' behavior after jailbreaks, mine wander, but not terribly far. I have worked very hard and long to get them to bond to me, and they more or less stay nearby, but I don't leave them unattended for more than minutes at a time*, and with the exception of a few "jailbreaks," they are in an enclosed area at all times. That is less to keep them close than it is to keep them alive. We have a long list of predators, daytime and nighttime, in our area. Others who have raised runners but less intensively, write that they do roam all over the place.
Their flying is what I would call wing-assisted jumping. They can get a foot or so off the ground and stay airborne for up to six feet, on a good day. Or they can scale a tilted fence while flapping their wings.
Take a look on youtube at amiga350. There are some video clips so you can see what they are like doing various things.
By the way (and you didn't ask this but I'll volunteer it). I love these birds!
ETA: * gosh that sounds like I never ever leave the property! I don't leave them unattended in the gardens for more than minutes at a time - when I need to go out, they are either in their basement shelter - in cold weather - or locked in their day pen/veranda/house complex. If I will be gone after dark, I either lock them in the house/veranda and turn on the electric fence, or have the ducksitter come by before dark and do that.