Galway man Tiernan O'Halloran returns to take his place at full back while Ronaldson is joined in the centre by the returning Bundee Aki. Matt Healy returns to start on the left wing while the half back pairing sees Jack Carty and Kieran Marmion line out together for the seventh time this season.
Up front, only Eoghan Masterson remains from last week, switching to Number 8 to allow captain John Muldoon return at blindside flanker, while Academy flanker James Connolly completes the back row.
Ultan Dillane and Aly Muldowney form the second row partnership behind the new front row trio of Finlay Bealham, Dave Heffernan and Ireland international Nathan White.
On the bench, both Ronan Loughney and AJ MacGinty have been passed fit for inclusion in this week's match day squad. Academy players Shane Delahunt, Sean O'Brien and Rory Parata are also included among the replacements.
Commenting on the team selection and the upcoming game, Pat Lam said:
"It's great to have players back available this week in what is going to be a really big test for us. Ulster have always been tough opposition and this weekend will be no different. When you look at what they have achieved already this season and what they are capable of, we know we will have to be clinical in everything we do to ensure we make the most of the opportunities we create.
"It's our first derby game at the Sportsground and there's going to be a huge crowd behind us. We are really excited to get out there on Saturday and determined to put in a performance that will keep our unbeaten home record intact."
Connacht team to face Ulster, Saturday December 26th, 18:00
15 Tiernan O'Halloran
14 Niyi Adeolokun
13 Bundee Aki
12 Craig Ronaldson
11 Matt Healy
10 Jack Carty
9 Kieran Marmion
1 Finlay Bealham
2 Dave Heffernan
3 Nathan White
4 Ultan Dillane
5 Aly Muldowney
6 John Muldoon (captain)
7 James Connolly
8 Eoghan Masterson
Replacements:
16 Shane Delahunt
17 Ronan Loughney
18 Rodney Ah You
19 Andrew Browne
20 Sean O'Brien
21 Ian Porter
22 AJ MacGinty
23 Rory Parata
Unavailable / Injured: Tom McCartney, Jason Harris-Wright, Denis Buckley, JP Cooney, Ben Marshall, Quinn Roux, Nepia Fox-Matamua, Eoin McKeon, John Cooney, Dave McSharry, Robbie Henshaw, Peter Robb, Conor Finn, Danie Poolman, Fionn Carr, Darragh Leader.
Connacht v Ulster
Saturday December 26th
The Sportsground
Kick off 6pm
Referee: Peter Fitzgibbon
Live on TG4 / BBC NI