Rosidae is a botanical name at the rank of subclass under the International Code of Botanical Nomenclature. Circumscription of the subclass will vary with the taxonomic system being used; the only requirement being that it includes the family Rosaceae.
The Phylocode definition includes Crossosomatales, Geraniales, Myrtales, Fabidae, Malvidae as they are defined in the APG III system. This definition was formulated in 2007, and is agnostic on the inclusion or exclusion of Picramniales and Vitales. Since 2007, the positions of Picramniales and Vitales have been clarified. The position of Picramniales as sister to Malvidae sensu stricto requires it to be included among the rosids.
In both senses, the term "rosid" applies, as an adjective and noun, to members of the group.
Subclass consisting of 116 families, and more than 60,000 species of angiosperms - the largest subclass in terms of number of families and about the size of the subclass Asteridae in number of species. They are more advanced than the Magnoliidae by being syncarpous and less advanced than the Asteridae by being largely polypetalous rather than sympetalous or having more than two fused carpels. The Rosidae has been distinguished from the Dilleniidae in that species with numerous stamens have the stamens initiated in centripetal sequence and usually do not exhibited parietal placentation which is common in Dilleniidae.
Molecular studies indicate that the Rosidae are a natural group only if a large portion of the subclass Hamamelidae and most Dilleniidae are included in it. The Proteaceae should be moved to the "lower hamamelids." The two orders Cornales and Apiales are related to lineages of the Asteridae as suggested by previous morphological and chemical studies. 
Relationship To Other Nonmagnoliid Dicotyledons
Parsimony analysis was used to develop phylogenetic hypotheses for Rosidae and other nonmagnoliid dicotyledons, especially Asteridae. Rosidae were placed among "lower" Hamamelidae as the sister group of Platanus and Hamamelidaceae. "Higher" Hamamelidae, Dilleniidae, and Asteridae nest within a paraphyletic Rosidae. With some expansion, the traditional Asteridae are monophyletic. For example, the problematic Columellia was placed among Asteridae as the sister group of Caprifoliaceae. Asteridae were placed as the sister group of Ericales among rosids circumscribed as Corniflorae in recent classifications of Dahlgren. Special attention was given to problematic groups that have been allied variously with Asteridae, Dilleniidae, and Rosidae. For example, Actinidiaceae and Fouquieriaceae were placed among Ericales. Loasaceae and Sarraceniaceae formed the sister group of Hydrangeaceae in the Corniflorae grade of Rosidae. Dilleniidae were not monophyletic. For example, Paeonia was placed as the sister taxon of the rest of the Rosidae, and Ochnaceae as the sister taxon of Linales. Dilleniaceae and Theaceae form a monophyletic group with Paracryphia placed as the sister group of Rhizophoraceae and Anisophylleaceae. 
Vernacular names of plants within the Sublass Rosidae
Common Mistletoes, Red Mangrove, anogeissus, aspalathus, balanites, beancaper, bittersweets, bladdernuts, buchenavia, buckeyes, buckthorns, caltrop, cicer, citrus, combretum, corynocarpus, creosote bush, crossosomas, currants, dwarf-flax, fagonbush, flaxes, geraniums, gooseberries, grapes, gunneras, hollys, horse-chestnut, legumes, leguminosae, lepuropetalon, lignum-vitae, loosestrife, mahoganys, malpighias, mangos, maples, melastomes, milkworts, nasturtiums, nemopanthus, oleasters, pea, peganum, proteas, puncturevine, radiola, ratans, sclerolinon, stonecrops, tamarind, touch-me-nots, wood-sorrels 
- Rosidae USDA, NRCS. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA. 29 January 2013.