The RRDi has been saying that carbohydrate is a rosacea trigger since 2004, especially sugar. However this isn't the first organization to say this even though carbohydrate and sugar still isn't on the NRS proposed trigger list that many physicians parrot when teaching their patients about rosacea triggers. Did your physician mention carbohydrate or sugar as a rosacea trigger? The RRDi has a much more extensive trigger list than the NRS and includes both sugar and carbohydrate.
As far back as 1896, Dr. Leviseur proposed carbohydrate limitations on his acne rosacea patients. Here is an excerpt from an article he wrote back then:
"There are a number of skin diseases which occur in connection with disturbance of the stomach and intestine. This fact is well supported by clinical evidence, but, viewed from the more elevated standpoint of theoretical science, it must be admitted that the true nature of this connection is far from being clearly understood….All writers agree that a large percentage of cases of acne rosacea is caused by indigestion…..These patients have factor ex ore, especially in the morning, sour eructations, constipation, and perhaps a distressing feeling of fulness after meals; in short, all the symptoms of a mild fermentative gastritis…..In severe cases lavage is indicated and has sometimes a surprisingly good effect on the skin eruption. It must not, however, be expected that the mechanical removal of the fermenting masses stops the fermentation; the latter will promptly start again with the very next food supply. Careful dieting is almost always necessary; the amount of carbohydrates should be limited; alcohol, tea pastry, the coarser vegetables and milk should be forbidden. Bismuth, carbonate of sodium, creosote, carbolic acid, thymol, and ichthyic may be employed. I have had good results from the use of fluid extract of ergot…..It would carry me too far if I were to consider the various drug eruptions which appear in connection with gastrointestinal disturbances, as for instance erythema after the use of quinine, antipyrin, turpentine, balsam of copaiba, sandalwood oil, arsenic, etc….." 
One recent paper remarked on this subject with the following about carbohydrate:
"The Western diet, which is rich in fat and carbohydrates and low in fibre, has altered the gut microbiome, which can lead to an impaired mucus layer and, in further stages, an impaired intestinal barrier. This contributes to an inflammatory state in the body that can be expressed as a skin pathology. Probiotics and diet manipulations have been successfully applied to (partly) restore skin disorders." 
Medical record, A Weekly Journal of Medicine and Surgery
Volume 50, No. 3, Whole No. 1341, New York, July 18, 1896, p 84, 85
edited by George Frederick Shrady, Thomas Lathrop Stedman
"A low-carbohydrate diet, but not a low-fat diet, reduces inflammation in patients with type 2 diabetes, according to research at Linköping University in Sweden." Source.
 Comput Struct Biotechnol J. 2021; 19: 624–631.
Skin microbiome transplantation and manipulation: Current state of the art
Chris Callewaert, Nastassia Knödlseder, Ante Karoglan, Marc Güell, and Bernhard Paetzolde,