The pair, calling a temporary truce in their battle for the 1992 jockey's championship, will join their American colleague in Portman Square as he attempts to initiate changes in racing's whip regulations.
Leading Newmarket trainer John Gosden will also be at the hearing to support Cauthen who - although facing punishment for breaking the rules at Goodwood last week - is in fact now leading a growing campaign which has sections of the Jockey Club on the defensive.
Roberts said at Brighton races yesterday: 'Steve asked Pat and I if we would back him at the inquiry. We are behind him all the way.
'The present rule ties jockeys' hands and I don't feel it is fair. It is also unfair to local stewards who must interpret the rule. The rule needs looking at and put under the microscope. It should be changed.'
Today's hearing is due to start at 2.30pm but Eddery and Roberts hope to be back in action at Kempton in the evening.
Cauthen was found to be in breach of the whip regulations for the first time in his career at Goodwood. He was suspended for four days for excessive and improper use of the whip on Witness Box but broke the rules a second time on Daru. Both horses are trained by Gosden.
The jockey is accused of striking each of the horses down the shoulder with his whip in the forehand position and in view of his opposition to the rule, the local stewards decided to let the Disciplinary Committee consider the second offence.
Cauthen faces an additional suspension of between four and 14 days if found guilty.
Discussions have already taken place between riders and Jockey Club officials about modifying instruction H9 that defines improper riding. It states that horses can only be hit on the shoulder, 'in very exceptional circumstances' if the whip is the backhand position.
Pat Eddery rode a double at Brighton yesterday on John Dunlop's Severine (7-2) and Chummy's Child (5-1) for John Sutcliffe. In the latter's race, Roberts finished unplaced on the 4-7 favourite, King Of Normandy.Reuse content