Vettel's charge from 15th on the grid to fourth meanwhile underlined Red Bull's current place in the pecking order.
The result extended Red Bull's Constructors' Championship margin over third placed Ferrari from five to 18 points following a lacklustre showing from the Italian squad.
Although teams develop their packages heavily in-season, form at the heavily downforce-dependent Spanish circuit is traditionally seen as a strong indicator of the season ahead.
“With Seb coming through the pack for fourth, it seems we have been the second best team in Spain,” noted Ricciardo post-race.
“I think it is still going to vary a bit, but maybe it will be a battle for that last place on the podium with me and Seb in Monaco, we will see.
“Monaco should be ok for us and hopefully we can get a bit closer to the Mercs there.
“It will be interesting and we will try as much as we can to catch them.”
The 24-year-old hopes to soon be used to standing on a Formula 1 rostrum
“I actually still feel a bit awkward up there, but I'm sure I will get more comfortable,” he said.
Ricciardo sits fifth in points after five races; six points behind Vettel.
Having struggled to adapt to the 2014-generation cars during the early part of the season, Spain proved a shot-in-the-arm for the four-time world champion.
The German has already downplayed suggestions that a podium is the only realistic target against the current might of the Mercedes.
“They have a very good package with the engine, car and two very good drivers,” he said of Mercedes following the Spanish Grand Prix.
“All in all that makes them so strong and difficult to beat.
“But it would be quite sad to go into the weekend and just aim for third.
“I think this weekend from the team point of view was good with third and fourth, but at the next race we'll attack again.”
Mercedes has scored an imposing 197 points to Red Bull's 84 ahead of Monaco.
Hamilton's four victories has the Briton three points ahead of Rosberg in the Drivers' standings, with the consistent Fernando Alonso (Ferrari) 51 points off the lead in third.