What do you mean "pick the panels for hosting"?.
I had a look at your model, its not all that complicated, but you have done half the work there by naming your work planes.

Did you try to DEFINE the work planes?

Define your work plane under the structural tab (at the far right) and pick one of your named planes (eg. Roof Plane Grid "C1" - "C2" BOD)
Now any steel framing you place, will place on this slope.

Don't forget to redefine your work plane once you are done.

I may be misunderstanding, but I'm able to attach geometry to your roof. I tested by attaching a beam system to the faces. I had no problems.

Karalon,

By panels I meant each individual sloping face of the roof. (2) of the sloped faces I could not pick the B.O.D. face for hosting the roof members for defining my work planes. The reason for the hosting the framing members to the roof is that this project requires the wood trusses and joists to parallel to the slopes. Normally I would just set a reference plane to my B.O.D. matching the slope but since the true pitch of this roof spans from opposite corners, causing all of the ridges and valley lines to be sloped as well I need the roof to host the framing members.

At any rate the reason why I could only pick (2) of the (4) B.O.D. faces was due to a discrepancy of the B.O.D. numbers I was given. The numbers were slightly off, thanks to rounding to the nearest 1/16th instead of the 1/256th causing a very slight twist in the B.O.D. Thanks for trying to assist me in this.

Barth,

No that was the problem I was having. I could attach framing to the first panel that I had modeled, the area in grid sector "1-2/B-C" but when I moved up to the grid sector "0-1/B-C" I was running into problems. If modeled that area flat I could pick it for hosting, but as soon as I adjusted the B.O.D. elevations to what I was supplied with the attachment would be lost. After working out the elevations in 2d I figured out that the datum numbers I was given for the B.O.D.'s were slightly off causing a little bit of twist in the roof. Were you able to host framing to all of the B.O.D. faces?

No, as a matter of fact I can't. But, I can catch all the faces individually if I make the construct a Floor using Modify Sub Elements, instead of a roof.

Im still confused as to why your structure cant host to reference planes.
Sure you need multiple planes, but each face will be parallel to the underside of each of the 4 different slopes.
I rarely host to another element, certainly not structural members, face based elements I would use for connection plates for example.

Anyhow, Im sure you have your reasons for adopting a different workflow, but workplanes although messy with multiple planes, should work without issue from what I can see. The best part is, that if that shape changes you just need to rotate your planes to suit and should be easy to make adjustments compared to face hosted you would need to delete everything and start over, for each change to slopes.

Karalon10,

In the past when I have had to model these roofs with a slope that spans between opposite corners of the a section of roof using a reference plane its caused some alignment issues, especially when the project is requiring the spacing measured on slope. Most time these issues have been a combination between keeping the framing members perpendicular to their bearing location while tilted to match the slope. This case in particular the spacing for the framing needed to be set such that at the bearing edges it measured 16" or 24" along the slope. That slope doesn't match the actual slope of the roof since the pitch of the roof was a combination of the a slope in bot the x and y axis. So for ease of modeling we will often model just the sheathing portion of the entire roof system for hosting it was just in this case that of the 2 of the 4 edges of one section of roof had a slopes that were not parallel by just a few 1/100's of degree. The workflow that I have I wouldn't have to delete everything and start over. They would need to be some clean up because things might shift or move a little bit during the slope adjustment but all work wouldn't be lost. Granted it may not function as cleanly when using a reference plane but in my experience this works best for us in maintaining accuracy.

Guys, if the roof construct is created using the Floor (not Roof) tool with Modify Sub Elements, Revit will then recognize ALL the faces of the resulting geometry. This will allow you to attach components – or Ref. Planes – or even Boundary Sketch Lines – to any or all of those faces. Mission accomplished. No?

Its really hard sometimes to comment on more complicated workflows, because often the devil is in the detail and until you really get in to try and model you can't see the immediate roadblocks to modeling.

"Most time these issues have been a combination between keeping the framing members perpendicular to their bearing location while tilted to match the slope."
I would have tried managing this using the "rotation" of the member, I have made a roof in the past on a curved/arc shaped metallic frame that then required purlins be placed on that curved slope, I handled this with offsets from a construction plane plus a rotation on the member. It worked just fine, but that said they were not also then sloping in another direction with a rotation but I would have probably tried it in the same manner.

It's also possible to model them as sweeps, just load in a profile for the correct steel member rather than tracing the profile, but this would allow you also some flexibility although would be a pain to change the sweep paths constantly with changes to roof if any....

Anyhow, it sounds like you have it sorted out actually, the error being in the calculation of the slopes...