Velz, John W. "'If I Were Brutus Now. . .':
Role-playing in Julius Caesar." Shakespeare Studies 4 (1968): 149-159.

Thesis: In the last paragraph of his essay, Velz sums up:
Role-playing is recurrent and striking behavior among the characters in Julius Caesar. The roles men deliberately choose to play delineate the opposed forces in the action and sketch the theme of Caesarism triumphant over political idealism. At the same time, there are other roles which men play without awareness that these are parts which other have played before them. This unconscious role-playing is one means by which Shakespeare draws Julius Caesar into structural coherence.  (156)
As one example of role-playing as a "recurrent and striking behavior" Velz mentions Cassius' comment, "If I were Brutus now, and he were Cassius, / He should not humour me." Another example is Antony's declaration to the plebians, that "were I Brutus, / And Brutus Antony, there were an Antony / Would ruffle up your spirits."

This is how Velz sums up his point about role-playing as representing "the opposed forces in the action":
Pompey, Marcus Cato, and Lucius Junius Brutus are, then, a triumvirate of republicans whose struggle against tyranny in the noble past is consciously re-enacted by Cassius, Portia, Young Cato, and Brutus. Balanced against these idealists who model themselves on a bygone heroism are those characters in the play who firmly committed to the decadent present which Cassius complained of and who successively assume the role of the tyrant, Caesar.  (152)
Velz's prime example of "other roles which men play without awareness" are the three instances in which characters other than Caesar offer themselves to be killed. Caesar does it first, when the mob cheers his refusal of a crown. Antony does it when he is negotiating with the conspirators. Brutus does it in his oration justifying Caesar's murder. Cassius does it in his quarrel with Brutus. According to Velz, Antony, Brutus, and Cassius are all re-enacting Caesar's role.

Evaluation: It seems to me that Velz extends his definition of role-playing so far that it ceases to have much meaning. A mere comparison of oneself to another doesn't amount to role-playing. And offering oneself to be killed is a recurring rhetorical move in this play, but I don't see how it amounts to role-playing in Velz's sense.

Bottom Line: Some interesting observations wrapped in a shaky theory.