Rose's circular (RTR) monogram was identified from a painting called "The White Peace", held in the collections of the Edinburgh City Art Centre.

"Watercolorist, etcher, engraver, illustrator based in London. Studied at the Slade School and Royal College of Art. Taught painting at the London Central School of Arts. Exhibited at the Royal Institute of Water Colours, Royal Academy, and Royal Society of British Artists. Biographical information: Houfe 484, Wood 485, Johnson and Greutzner 515." - From The Digital Victorian Periodical Poetry Project

The C does not have a serif, and the M fills the entire space, touching the top and bottom curves of the C. The opening of the C is quite small, when compared to the other monogram also called "M inside C".

A cartoonist known primarily for the cartoons he did for Judy (1875-1889) and Punch (1868-1879).

C with an intersecting M and S inside of it

Possibly George Waters (1863-1947), the Irish lithographic artist referenced here: https://artuk.org/discover/artists/waters-george-18631947

She is often credited as "Mrs. Percy Dearmer" in publishers advertisements and in the books she illustrated.

Bertha was an artist from Boston who illustrated many children's books and also designed some covers for the same. Until she married Edward E. Hoxie, she was credited (and signed her work as) Bertha G. Davidson, and sometimes used a "D" monogram, or a "BGD" monogram.. After her marriage, she was credited either as "Bertha G. Davidson", "Bertha Davidson Hoxie", or just "Bertha Hoxie". Her monogram also seems to have changed to an "H" or "BDH" at that point.