The easiest answer is that, much like the invention of guns & explosives, the discovery of evolution is not inevitable. It took humans until the 1800's to really pin down a solid theory, so it's conceivable that this alien culture just happened to perfect space travel before discovering evolution.
The problem with that idea is that the invention of space travel and the discovery of evolution both have the same root cause: a society that values discovery, progress, science and exploration. If you want to get into space, you need a highly STEM-advanced civilization, and that makes it very likely that you'll find out about evolution just as a side-note.
Religious creationism - on its own - can't top this. The theory of evolution would have been discovered and accepted by the scientific community, assuming the world these people come from is enough like our own, and even if religion tries to stamp it out as heresy, they're still aware of the concept.
Oh, and as to the idea that they don't know about evolution because they're robots? No. Artificial intelligence is still subject to natural selection, so they would have diversity of what stands for life, it would just be intelligently designed for optimization as opposed to gradually culled for adequacy. Even if you can argue that's not the case, it's kind of a lazy explanation.
But there is a way for life as we know it to have space travel without the theory of descent from common ancestry:
The alien civilization is post-apocalyptic.
Let's say that these aliens, much like in real history, started to develop guns and explosives before the scientific age. They would have basic rockets and be familiar with the concept of attaching a payload, because they can make better weapons that way.
Then calamity struck. Their planet had a dust-ring that started to collapse because of the gravity of a passing planetoid or falling moon, which will itself eventually impact the planet. In the meantime, the surface is pelted with life-threatening impactors from the dust ring.
This impending doom necessitated mass exodus to the planet's habitable moon through the construction of basic rockets, like the ones that took humans to Earth's moon, but on a much larger scale.
The moon is habitable, but has no native life, and by the time the rocks have stopped falling, the main planet is uninhabitable. The moon-men, their livestock, and their crops are the only living things in their world, all of which are greatly genetically diverged from each other. From this small sample size of maybe dozens of species, it's hard to come to the conclusion that they are all descended from common stock, and there's not much reason to go back to the hellscape that was once their ancestral home.
Throughout that whole ordeal, the 'aliens' had no collective time or interest in biodiversity aside from the bare minimum they needed to set up a survivable colony, and that's an exercise in agriculture more than science.