Captain Joshua Stevenson increased the lead to 2-0 in the 49th minute before the hosts found the net in the 73rd minute from their left winger.
Centreback Robertson reiterated Stop Out were a formidable force so claiming three points on their turf wasn't an easy task.
"Our first half performance was good and, for the large parts of the second half, we'd probably liked to have been a little more clinical to finish the game off."
He said his troops showed character in holding off the hosts.
Stop Out player Jordan Martens collected his second yellow card of the match in the 88th minute and was sent for an early shower.
It was pretty good conditions to play in the capital city, he said, although the ground was "a little bobbly".
"It's not the worst we're going to play on but, yeah, it was fine."
Wellington United beat Waterside Karori 5-3 yesterday at Newtown Park while Suburbs thumped Wellington Olympic 3-0 at Endeavour Park.
Robertson said Wellington United appeared to have a strong line up, with just one loss last weekend to Wairarapa United, so they should be regarded as contenders for the league crown.
"They'll be there or thereabouts to challenge for the league title with their link with Wellington Phoenix with some good, young players so it'll be another great test for us back at home."
He suspected the Wellington United players would bring a more possession-based type of football than the more direct challenge from Stop Out yesterday.
It would be another similar test to the Western Suburbs one, he said.
