Doc,
Yes we do have two people on board road trains, a conductor and engineer. Usually if you see anything more than that, that means that either the conductor has a student or the engineer has a fireman (that's what we call engineers-in-training out here). We only have people riding in the rear units (the ones directly behind the lead locomotive) that are deadheading, meaning they're going to work another train at the away from home terminal or there are no scheduled trains at their away from home terminal.
I'll give some examples to help out. For instance, my normal run on the road is from Cheyenne to Rawlins, WY and return. Nothing more or less. Say they have a bunch of oil coming out of the refinery at Sinclair, WY (seven miles east of Rawlins) it'll be tacked onto all the eastbound trains stopping in Rawlins via the Sinclair local. Since there's a little demand going west but a heavy demand going east they may not have enough rested crews in Rawlins to take a train to Cheyenne. So they'll deadhead, sometimes by van or sometimes by train. When the weather gets bad most times it'll always be DHing by train due to going over "The Hill" east of Laramie. Basically it's just a ride to where work needs to be done. Same thing vise-versa, if there's a lot of westbound freights with few trains heading east you could catch a DH back home.
Now let's talk about yard trains. You have two different types of yard jobs, the remote and conventional. Currently I'm a FRA Class 6 license holder, meaning I can operate a remote control locomotive. Essentially it's DCC in 1:1 scale. With RCL there's a foreman and a switchman with nobody in the cab of the locomotive controlling it. Both F&S have the "beltpack" strapped on a special vest. Here's said beltpack:
View attachment 146400
This enables either person to transfer control to each other for protecting shoves. Say if I was on the switch lead lining up switches for our next move and the foreman was on the point protecting the shove into the yard track, after he gets done running into the track he can "pitch" it to me to protect the shove coming out of the track. Kinda like stealing a locomotive on DCC. Conventional jobs actually have an engineer as well as foreman and switchman and are usually used for jobs that leave the yard to service an industry but are not considered a local. In Cheyenne we have the YCY52 (Y-yard job, CY- station name for Cheyenne, 52-identification number) which is the conventional switch job that heads out to Dyno Nobel to service that industry as well as take on east end yard switching. Top speed with RCL is only 15, further reduced to 10 mph in the yard on most tracks (some are 5) but with a conventional yard job you can operate at track speed. Hence the difference.
From what I understand, most other railroads use the same lingo as UP, and UP has set the standard for a lot of rules and operating practices. Also working for them I know how modern freight moves now.