Magazine  (2018)  Page(s) 54.  Includes photo(s).
 
[From "„...vff der frůcht ein schwartz hütlin.“ Zur Geschichte und Verwendung der Wildrosen", by Tobias Niedenthal and Petra Rothütl, pp. 54-58]
Für das folgende frühe Oligozän, also die Zeit vor 34 bis 28 Millionen Jahren, gibt es aus den heutigen US-Bundesstaaten Colorado und Montana Funde der fossilen, nach Charlotte Hill benannten Rosenart Rosa hilliae.

Translation:
For the following early Oligocene, i.e. the period 34 to 28 million years ago, there are finds of the fossil rose species Rosa hilliae, named after Charlotte Hill, from what are now the US states of Colorado and Montana.
 

Article (magazine)  (1963)  Page(s) 99, 104, 106.  
 
p. 99: Leo Lesquereux in 1883 described the first American rose from the Oligocene Florissant beds in Colorado, naming it Rosa hilliae. Subsequently, many apparently different forms were discovered in the United States and elsewhere, and a deluge of new species names were applied. Chaney (1927, p. 123) suggested that Rosa hilliae be made a form species by incorporating the following undoubtedly identical forms: Rosa wilmattae Cockerell (leaf), R. scudderi Knowlton (leaf), R. inquirenda Knowlton (calyx), and R. ruskiniana Cockerell (bud). MacGinitie (1953, p. 121), in his ‘‘Fossil plants of the Florissant beds in Colorado", concurred by upholding the synonymy. Nevertheless, new species names appear in literature with scant regard for morphological or variational similarity to the American form species.

p. 104: Rosa hilliae (figs. 1-6; 11-14 ; 50-59) from the Oligo-Miocene, as the priority type of the American group, should include the Miocene R. miocenica Axelrod, the Oligocene R.? inguirenda Knowlton, R. scudderi Knowlton, and the Paleo-Eocene R. cetera Hollick and R. confirmata Hollick from Alaska.....

p. 106: There is unanimous agreement that Rosa wilmattae Cockerell (1908) (fig. 7) and R. scudderi Knowlton (1916) (fig. 8), both from Florissant, are identical with R. hilliae. The fossil record of the Oligocene Ruby paper shales fully confirms this conclusion. R.? inquirenda Knowlton (1916) (fig. 9) represents a pentamerous calyx which is doubtfully assigned to Rosa. Since this specimen is a Florissant fossil, as is Lesquereux's R. hilliae the calyx, if it is of a rose, should be properly assigned to R. hilliae. The same reasoning applies to the bud impression of R. ruskiniana Cockerell (1908) (fig. 10), also from the Florissant

Book  (1883)  Page(s) 199, pl. XL.  Includes photo(s).
 
FLORA OF THE GREEN RIVER GROUP
ROSA, Linn.
Rosa Hilliæ, sp. nov.
Plate XL, Figs. 16, 17.

Leaves small; leaflets oval, obtuse or short-pointed, serrate; stipules large, lancelolate, acuminate; nervation camptodrome.
These beautiful small leaves represent this genus more distinctly than any of the other fossil leaves which as yet have been referred to it. The leaflets are rather obtuse, the lateral much smaller, 5 to 15 millimeters long, 3 to 7 millimeters broad — all short-pediceled like the terminal ones; the nervation is camptodrome, the figure shows it mostly craspedodrome, a mistake evidently, for as seen on the left side of the largest pinnule, fig. 16, the veins are curved. The nervation near the borders is not quite distinct on the specimens.
Hab. — Florissant. Princeton Museum, No. 768. Also in the collection of the U. S. Geol. Expl. by Dr. F. V. Hayden.