It was refused because it was seen as out of keeping with the conservation area and area of outstanding natural beauty.
The site is within the Ross-on-Wye Town Conservation Area and the Wye Valley Area of Outstanding Natural Beauty.
A previous application for the garden room was withdrawn and this revised scheme is on a different site, nearer to the public house.
The Ramblers Association objected to the proposal feeling it was not in keeping with the AONB or conservation area.
Herefordshire Council's conservation manager objected to the proposal with regard to its size, design and materials.
Ross-on-Wye Town Council had no objections.
Two letters of representation were received from a resident and Ross-on-Wye and District Civic Society saying the garden room would be a monstrosity and a visual intrusion to users of the public footpaths.
The applicant, in a design and access statement, said the development was necessary for the continued profitability of the public house and would help to create more business in the quieter winter months.