I'm doing a new build as well, so i'm no expert, but it sounds like your symptoms are similar to what I was experiencing. I'm building a Kossel, which should be close to a rostock if I remember right.
Have you checked the voltage on your stepper drivers? I think that may be related to the motor moving fine in one direction but not the other.
when Pronterface moves the print head you can expect all 3 motors to work in conjunction to move the effector platform (I think that's the right term) since it has to keep it level through the whole motion. the LCD may be just testing the single motors, I'm not sure. my LCD (Gadgets3d) and RAMPS1.4 using builda3dprinter.eu's firmware mobilizes multiple motors to move the printhead/effector platform.
hope this helps, or that you'd already got it fixed!
Have you checked the voltage on your stepper drivers? I think that may be related to the motor moving fine in one direction but not the other.
when Pronterface moves the print head you can expect all 3 motors to work in conjunction to move the effector platform (I think that's the right term) since it has to keep it level through the whole motion. the LCD may be just testing the single motors, I'm not sure. my LCD (Gadgets3d) and RAMPS1.4 using builda3dprinter.eu's firmware mobilizes multiple motors to move the printhead/effector platform.
hope this helps, or that you'd already got it fixed!