The parentage given here is provided by Dr. Svejda in diagrams on pages 43 and 41 of her book
The Canadian Explorer Roses (National-Roses-Canada, 2008).
In September 1998, the Montreal Botanical Garden (Le Jardin Botanique de Montreal) carried out a survey of its roses' resistance to black spot, powdery mildew and rust. This is one of the outstanding varieties which showed a 0% to 5% infection rate. The data were taken on well-established roses.
From the Internet, a report on the cold-hardiness of this rose: 'William Baffin' performs beautifully in the harsh conditions of the Rocky Mountain West. In our garden, the canes are completely winter hardy in Zone 4 at 8,500' altitude without mulch or snow cover. Tolerates the dry heat in the summer without flinching.
And another happy grower reports: I've grown this rose in northeastern South Dakota with no winter protection for 3 years now and it's been completely hardy. We are on the northern edge of Zone 4 with temps dropping to -30F or lower at times.
One of the Roses that "passed the test" in Longwood Gardens' Ten-Year Rose Trials.