The first red halted proceedings for 11 minutes when Felipe Nasr crashed heavily on the back straight. The Brazilian lost the rear end of his Sauber while weaving to get heat into fresh tyres and nosed the car into the wall, leaving his mechanics with a race against time to repair it in time for qualifying.
The second and final stoppage came after Jenson Button parked his McLaren on track with suspected engine problems, which could rule him out of qualifying.
After all the drama, Romain Grosjean again found himself near the top of the order, with third place for Lotus. Valtteri Bottas was fourth for Williams, followed by Force India’s Sergio Perez and Red Bull’s Daniil Kvyat.
Mercedes opted not to head out for most of the first half of the session, but when they did emerge Rosberg went fastest with 1m 16.762s. Hamilton, however, locked up going into the hairpin and didn't better 1m 21.779s on the soft tyre, which left him down in 19th place.
Raikkonen had just pipped Rosberg with 1m 16.761s when Nasr speared into the wall, triggering a lengthy stoppage as the remains of the blue and yellow car were cleared up.
When it resumed - with Raikkonen, Rosberg and Grosjean covered by just 0.011s at the top - it became a shootout on the supersoft Pirelli tyres. First Raikkonen improved, with 1m 16.233s, before Rosberg then flattened Ferrari with 1m 15.660s.
But it wasn't all good news for Mercedes, as Hamilton missed the entry to Turn 1, scuppering his lap. That proved costly - Button rolled to a halt on the exit of Turn 7, the reds flew once more, and the session came to a premature close, leaving the Silver Arrows book-ending the timesheet, with the world champion down in 20th place on 1m 21.492s.
Grosjean was another who didn't get the chance to improve, but Lotus had to be happy with his 1m 16.772s which remained good enough for third ahead of Bottas on 1m 16.914s, Perez on 1m 19.993s, Kvyat on 1m 17.021s, Massa on 1m 17.122s, Vettel on 1m 17.197s, Carlos Sainz on 1m 17.396s, Pastor Maldonado on 1m 17.573s, Marcus Ericsson on 1m 17.578s, Nico Hulkenberg on 1m 17.876s and Daniel Ricciardo on 1m 17.892s. Six different teams therefore filled the top six, while less than one second covered third through to 12th.
Nasr was 14th on 1m 18.446s, then came Button with 1m 18.473s and Max Verstappen on 1m 18.492s. The Dutchman's Toro Rosso had a new Renault engine installed, and since it was his fifth of the year he is set for a 10-place grid penalty to add to his five from Monaco. No prize for guessing where's he's likely to start tomorrow...
At the rear of the field, Marussia sandwiched McLaren's Fernando Alonso, who didn't emerge until the final 11 minutes due to his own engine change. Will Stevens reasserted himself over team mate Roberto Merhi with 1m 19.822s to 1m 20.231s, with Alonso 18th on 1m 19.874s - two spots ahead of Hamilton.
The mixed order means qualifying will have even greater intensity than usual as everyone tries to make up for lost track time while still learning how to get the best from their rubber...