Less than half a second separated the trio at the close of play, although it was Nasr who set the headline time as he bolted on Pirelli's super-soft tyres and lapped the Spanish track in 1m 21.545s. The Brazilian also clocked up more than 100 laps on what was only his second official session as a Formula One race driver.
"It was another positive day," Nasr reflected. "We did a lot of mileage, and we were able to get a better understanding of the car. On top of that, we used different tyres in different conditions, and we played with the set-up. Overall they were two very positive days. I'm glad that I already feel comfortable in the new environment, and I'm really happy with everything I've seen so far with the team."
Raikkonen maintained Ferrari's position at the sharp end of the times with a 1m 21.720s on the white-marked medium compound, which was enough to edge Rosberg by two-tenths of a second in the fight for second overall.
"It's too early to talk about results, but we are going in the right direction," Raikkonen said. "There is still a great deal to do, however this has been a positive start, very different to a year ago. A good job has been done on the car with a lot of improvements."
Elsewhere there was encouragement for McLaren as Fernando Alonso managed 32 laps total, and several multi-lap runs, on his final day of running at Jerez.
The Spaniard's day was cut short by a loss of cooling water pressure, which left him with an unrepresentative time of 1m 35.553s set in mixed early conditions. Nevertheless the team were buoyed by their increased running relative to the first two days, and also by the fact they will be able to replace the problematic components ahead of the fourth and final day.
"This morning, it was a relief to see the car get out of the garage at 9am, and run without problems for several hours," McLaren racing director Eric Boullier said. "Fernando's comments were very positive, too: he said the car was reacting well to changes, and felt stable. Operationally, we've already covered everything in our programme, but what's even more positive is that we've been able to carry out a number of longer runs. They've shown us that the car doesn't have any conceptual or architectural issues."
Alonso's tally was still in stark contrast to Rosberg, who once again set the standard with 151 laps in the Mercedes F1 W06 Hybrid. The German's day included triggering the red flags when an on-track engine shutdown brought him to a halt just after midday.
Nasr had earlier triggered the red flags to fly when he spun into gravel at Turn 9 in damp conditions, while Lotus's Pastor Maldonado brought them out for a third time with just over one minute of the day remaining when he stopped out on track.
The Venezuelan had been delayed as Lotus encountered telemetry problems in the morning, but eventually finished the day fifth overall - just behind Felipe Massa, who took over from Valtteri Bottas for his first day of running in the Williams FW37.
"The feeling in the car was good even for a first impression and it's well balanced," Massa explained. "I am also confident in the car set-up. The FW37 is another step forward from where we left the FW36, which is promising."
Carlos Sainz Junior was sixth for Toro Rosso, while Daniel Ricciardo was limited by engine problems that restricted Red Bull to a handful of short runs in the RB11 as the day drew to a close.
"Although we were limited with running today, we got some long runs together and that was encouraging," Ricciardo said. "In terms of where we're at, it's impossible to know about the pace because we don't know what people are running, but I think the consistency today was good, we put a few laps together in the end, so a few positives to take away from today.”
Testing concludes at Jerez on Wednesday.
Unofficial Tuesday testing times from Jerez:
1. Felipe Nasr, Sauber, 1m 21.545s, 109 laps
2. Kimi Raikkonen, Ferrari, 1m 21.750s, 94 laps
3. Nico Rosberg, Mercedes, 1m 21.982s, 151 laps
4. Felipe Massa, Williams, 1m 22.276s, 71 laps
5. Pastor Maldonado, Lotus, 1m 22.713s, 96 laps
6. Carlos Sainz Jr, Toro Rosso, 1m 23.187s, 137 laps
7. Daniel Ricciardo, Red Bull, 1m 23.901s, 49 laps
8. Fernando Alonso, McLaren, 1m 35.553s, 32 laps