One thing should be noted about RPI: most of our residence halls have not been updated in a while.
If the distance from the Lally School building (Pittsburgh) is the most important to you, then room in Blitman Residence Halls. It is the closest to the Lally School building (Pittsburgh) but it does not have singles, there are only doubles.
If having a single room is the most important to you, then consider rooming in Quad. It is the second closet to Pittsburgh and has singles.
Private bathrooms for single rooms are scarce in Quad. If you want that you will have to go much further away from the Lally School building.