The Nucor mill near us is a true mini mill. I don't think they roll any structural shapes larger than a W6x15 and only up to 6" angle and the larger sizes you get above 3x3" angle they have a schedule of when it's rolled. From the last list I saw a lot of it was misc. stuff. 1-1/2" and 2-1/2" angle and stuff. We never use any of that stuff except a lot of w6x15's and 3x3x3/8 angle for clips and some 6x4 angle for circular platforms. No idea who uses the 1-1/2" misc. sized angles but I think that type of stuff is the majority of stuff they roll.
Used to do work for a company outside of Houston that made grating. They bought steel coils by the trainload and have several waiting to unloaded on their spur all the time. They had a machine they had made that uncoiled and burned the plate into what would normally be long ass flat bar, turn it up, notch it, for making grating by the truckload. They went out of business but their super giant competitor was 45 minutes away.