Roger Mortimer vs Roger de Mortimer

Roger Mortimer and Roger de Mortimer both are nouns.

Word	Noun	Adjective	Verb	Adverb
Roger Mortimer	Yes	No	No	No
Roger de Mortimer	Yes	No	No	No

As nouns, Roger Mortimer and Roger de Mortimer are synonyms defined as:

Roger Mortimer and Roger de Mortimer: English nobleman who deposed Edward II and was executed by Edward III (1287-1330)

Other synonyms of Roger Mortimer include Mortimer.

Roger Mortimer (noun)	Roger de Mortimer (noun)
English nobleman who deposed Edward II and was executed by Edward III (1287-1330)	English nobleman who deposed Edward II and was executed by Edward III (1287-1330)