Bastianelli and Blaak thwarted van Dijk's surge after the final stretch of cobbles, bridging to the Dutchwoman with around four kilometres to go.
The trio then worked together to keep the chase group at bay, the European champion with just enough left in the tank to take the win on the line.
"I'm very happy. It was very hard day today, I am happy for the win this day and I think it's nice for me and the team," Bastianelli who now leads the UCI Women's World Tour, said.
Van Dijk's attack at under 10 kilometres to go capitalised on a mistake by Australian Grace Brown who led the race for 50 kilometres until taking a wrong turn 15 kilometres from the finish.
Her team mate Gracie Elvin, looking strong and positioned nicely in the main bunch as they flew past Brown, punctured with 13 kilometres to go, taking her out of contention.
Despite her wrong turn, Brown appeared chuffed about spending 50 kilometres at the front of her first ever Women's WorldTour cobbled classic, although it wasn't the plan.
“The second time over the VAMberg at about 100km mark we wanted to reduce the peloton by putting pressure on over the climb," Brown explains. "I found that I had a bit of a gap on the top, so even though it wasn’t our plan we decided to work with it to keep Gracie and Roy in a good position.”
“I never actually thought that I would be able to make the distance. Even when it got out to two minutes, I was tiring a lot and I knew that the peloton would eventually close the gap. But I just kept going knowing that it was a good situation for the team.”
“The peloton were only a few seconds off me when I went the wrong way at a roundabout. I’m not exactly sure what happened there!”
“Gracie’s puncture was super misfortunate. She was in a great position on the last cobbled sector and had good legs. It looked like we were going to pull something off. Hopefully she can take confidence towards the next races despite the bad luck, because she’s obviously in awesome form at the moment.”
(And yes, that is a vaccuum cleaner former road world champion Blaak received for finishing second):