During the early Renaissance, a publication would use either roman or italic type, not both. Today, roman and italic type are mixed, using roman for most of the text and italic for special purposes. Most typeface families include, at a minimum, roman, italic or oblique, and boldface character sets.
Nesbitt, Alexander The History and Technique of Lettering (1957), Dover Publications, Inc.ISBN 0-486-40281-9. The Dover edition is an abridged and corrected republication of the work originally published in 1950 by Prentice-Hall, Inc. under the title Lettering: The History and Technique of Lettering as Design