Riordan impressed last weekend for Buccaneers, scoring two tries in their AIB League Division One win over Dungannon.
In the injury-enforced absence of John Muldoon, Gavin Duffy will captain Connacht once again.
Duffy started at full-back in last Friday's 53-13 Magners League defeat to Ulster but has been moved to outside centre for the trip to Rovigo, with Fionn Carr reverting to full-back.
As well as Deane and Muldoon, Connacht have Liam Bibo (hamstring), Andy Dunne (knee), Joe Merrigan (knee), Conor Muldoon (hamstring), Colm Rigney (knee), Mike Roberts (calf) and Niva Ta'auso (arm) on a lengthy injury list.
Connacht will be hoping to get back to winning ways this weekend after leaking seven tries at Ravenhill. They are currently second in European Challenge Cup Pool 1, six points behind leaders London Irish.
This will be the westerners' second European meeting with Rovigo. They beat the Italian Super 10 side 21-20 on their last visit to the Stadio Mario Battaglini in October 1998.
Rovigo are currently fourth in the Italian championship and their recent run of results includes a 24-23 success over second-placed Viadana.
CONNACHT (v Rugby Rovigo): Fionn Carr; Troy Nathan, Gavin Duffy (capt), Keith Matthews, Danny Riordan; Ian Keatley, Frank Murphy; Brett Wilkinson, Sean Cronin, Robbie Morris, Andrew Browne, Andrew Farley, Michael McCarthy, Johnny O'Connor, Ray Ofisa.
Replacements: Adrian Flavin, Ronan Loughney, Michael Swift, David Gannon, Kieran Campbell, Tim Donnelly, John Hearty.