rhankc
I think you are misunderstanding how to enter the roof 'slopes'. It is done differently for hip/mansard and gable/pyramid roofs.
For a hip or mansard/sprocket roof you can only enter the roof slope as an angle in degrees [a number] e.g. 22.5, OR the slope as a ratio [separated by ':'] e.g. 2:5. For these types you CAN'T enter a ridge/apex height using a ^. If you do it should return an error thinking you've entered zero degrees
For a gable or pyramid roof you can enter the angle or ratio as above OR additionally you can specify the ridge/apex height above the fascia in current units by prefixing it with a ^, e.g. ^1234 (here assuming mm this puts the ridge/apex at 1234mm high). Don't use a units suffix or try '/" - so 1234.5 (in mm) is OK as is 18 (in inches) or 1.5 (in feet) but NOT 1'6".
When you make a hip or mansard you need to have one horizontal face selected otherwise you'll get error messages.
When you make a gable you need to select one face that's both horizontal and forms a rectangle, AND also select an edge that's near where you want the 1st gable to be (that's needed to tell the tool which of the rectangle's sides are to form gables and which of them is the 1st one, since you can apply different settings to the 1st and 2nd gables).
When you make a pyramid you need to select one face that's both horizontal and forms a rectangle, AND also select an edge that's on a side where you want the angle for the slope to be taken from - with a non-square pyramid the two pairs of opposing faces have different slopes so you need to do this to indicate which gets the degrees/ratio you've given. Note that you need to select one of this rectangle's edges even if you intend later to use ^1234 as the height of the apex instead of entering degrees or a ratio, as at the point where you set off the tool has no way of knowing what options you might choose later...
Your item about it saying inches in the menu prompts and it showing it in feet is a function of SketchUp: if you are working in Architectural units - inches - and you enter 18" it's taken OK but when you reopen the dialog it will show 1' 6" - the prompt simply tells you that your current units are set to inches [or feet or cm or whatever] - SketchUp displays Architectural inches as feet+inches if it's >12".
