The move comes as the firm shakes up corporate and financial comms ahead of a listing on the London Stock Exchange.
Riley left Aviva last week and is to join Resolution on 6 June. He is briefed with preparing the company for the listing, which is to take place within the next two years.
Resolution has also hired Jim Newman, finance director of Aviva subsidiary Norwich Union Life. He joins in October as group financial controller.
Resolution CEO Clive Cowder said that while there were no immediate plans to pitch the corporate account held by Financial Dynamics, the firm would review all advisers as preparations for its IPO get under way.
In February the group appointed Temple Bar Advisory, the one-man media and IR shop founded by former FD managing director Alex Child-Villiers, to handle aspects of corporate PR.
A said Resolution was reviewing FD's role as adviser.
Resolution was set up last year with the backing of life assurance companies including Prudential and Standard Life.
The company is one of several trying to unlock value from the £160bn invested in closed (or capped) life funds in the UK.
WPP's PR and public affairs sector firms, which also include Burson-Marsteller, brought in £117.1m in the three months to 31 March, up from £105.3m for the same period last year.
Increases from PR and public affairs contributed to an overall rise in group revenue of 16 per cent.
WPP said the hike in revenue was partly due to the inclusion of figures from Grey Global, which owns GCI Group. But likefor-like revenues without Grey Global were still up by almost six per cent.
WPP said the figures showed a continued improvement in organic growth and proved that clients were increasingly 'improving profitability through innovation, branding and top-line growth, rather than by relying solely on cost cutting'.