Westlake broke the scoreless tie at 7:33 of the second period, ripping a shot upstairs from in tight for his second goal of the tournament.
Canada had a number of chances to extend the lead but was forced to hang on late as the Czechs made one final push in the dying seconds.
"They're a big team. They're physical," said Westlake. "They've got a lot of men on their team.
"It's a lot of cycling against the Czechs. They have a big goalie so you have to pick your spots. If you're not shooting the puck well it's going to be a low-scoring game."
Canada has surrendered just one goal on 18 shots through three round-robin victories while outscoring its opponents 15-1.
"It was a fun game to play and it was a necessary game to play because we get better and we needed a team to push us going into the medal round," said Westlake.
Czech goalie Michal Vapenka stopped 17 shots in defeat as his team was eliminated from the competition.
"We had some scoring chances, there was just no finish," said Canadian head coach Mike Mondin. "The kid in net is a good goalie.
"He's a big guy so they're trying to go high and we shot a lot of them over the net."
Canada clinched first place in its pool and will take on the United States in one of Thursday's semifinals. The Americans, who won gold four years ago in Vancouver, dropped a hard-fought 2-1 decision to the host Russians earlier Tuesday to finish second in their group.
Russia will meet Norway in the other semifinal.
Canada won Paralympic gold back in 2006 but had a disappointing fourth-place finish in 2010.
Elsewhere on Tuesday, biathlete Mark Arendz battled pouring rain and dense fog to win a bronze medal in the men's 12.5-kilometre standing category.
It's the second medal of the Games for the native of Hartsville, P.E.I., who captured silver earlier in the week.
He finished in 30 minutes 31 seconds. Russia's Azat Karachurin won gold in 29:30.0 while Norway's Nils-Erik Ulset captured silver.
"To get a medal is awesome and that was the goal," said Arendz. "There were mistakes out there both in shooting and on the course so it was not a perfect race, but any time you are on the podium I have to be happy because this is strong field."
Arendz's medal was Canada's seventh so far in the competition (one goal, two silver, four bronze). Host Russia continues to lead with a whopping 34 medals, 23 ahead of second-place Ukraine. Canada and the United States are tied in third.
Arendz, who shot 19-of-20, said the poor visibility made the race extra challenging.
"It was the same conditions for everyone," he said. "I wasn't perfect in shooting so I know there are still mistakes that need to be cleaned up."
In para-alpine skiing, Braydon Luscombe of Duncan, B.C., was the top-placing Canadian, finishing second in the standing division with a time of 52.17 seconds. Josh Dueck of Kimberley, B.C., placed fifth in the sitting category in 59.93 seconds.
Standing athlete Kirk Schornstein of Spruce Grove, Alta., was 17th and Mac Marcouxopf Sault Ste. Marie, Ont., and guide Robin Femy of Mont-Tremblant, Que., did not finish their run in the visually impaired category.
Sit-skiers Caleb Brousseau of Terrace, B.C., Calgary's Kurt Oatway and standing athlete Matt Hallat of Coquitlam, B.C., also did not finish.
In the women's slalom, standing skier Calgary's Alexandra Starker was the top-placing Canadian in 1:06.59. Toronto's Erin Latimer was eighth.
In wheelchair curling, Canada improved to 5-1 and moved into a first-place tie with Russia with an 8-5 victory over China.