In his new role, Robertson oversees a team of 50 ad specialists, and is responsible for managing the advertising process from start to finish, according to his LinkedIn profile.
He will now manage creative ideation through to delivery of completed campaigns for both brands in multiple markets.
Robertson, a Paddy Power veteran of at least 16 years, was formerly director of brand engagement for the betting company until April.
He has held a number of roles within the business, including head of mischief between 2011 and 2014.
Paddy Power confirmed Robertson's new role.
Robertson's promotion comes after a wider shake-up at Paddy Power Betfair, with the departure of Paddy Power's chief marketing officer Gav Thompson.
Thompson's exit was understood to be due to the £5bn merger, and he has been replaced by Betfair CMO Jonathan Devitt, who now holds that role for the combined entity.