Just to clarify, Wyze does not source anything from Xiaomi. Xiaomi does leverage some of of the same ODM suppliers as Wyze does (note there is a difference between ODM and OEM).
Honestly, the majority of companies that make physical products, particularly IoT, tend to partner up with a 3rd party supplier and do “ODM” manufacturing. Some of them will pay the supplier for an exclusive right to it, while others don’t. Believe it or not, even Apple, Samsung, Amazon, and many, many more rely on 3rd party ODM suppliers to make their devices, rather than doing it all themselves. It’s highly normal in the tech industry.
For example, the iPhone is actually manufactured by Foxconn, not “Apple” and Samsung Smartphones and Tablets are actually manufactured by companies like Wistron and Foxconn too. Amazon uses TONS of different ODM suppliers for their various things.
Wyze is no different. They have multiple different ODM partners for various Wyze devices. Some of them they have helped design themselves, and some of them they have exclusive rights to the design so others can’t use them, but others, they don’t care if other companies use the same or similar design because Wyze maintains a huge advantage in all the added firmware features, etc that they personally add to it in-house that they others don’t have. A famous example is the Wyze V2 camera vs the Xiaomi camera that looked identical to it. The Wyze one was FAR superior with tons more features and a lot better because Xiaomi basically just kept the stock firmware, while Wyze made it tons better for several years and still cheaper. So despite the fact that they used a similar ODM supplier (Hualai), Wyze was tons better.
Talking about Roku, that is different…Roku and Wyze have a totally different relationship/partnership where Wyze provides them with their smart home tech…Wyze isn’t their ODM, but there is a different kind of partnership there that is similar in some ways.
I do find it funny that a lot of people who argue about brands don’t realize that in some cases they’re both supporting the same supplier, like with iPhones vs Samsung devices often both coming from Foxconn/Han-Hai. Same with a lot of HP vs Dell both coming from Foxconn/Han Hai 
So I always get a little bit of a giggle over such debates because of the underlying subtext of them often actually being made by the same company/supplier and how in a way they’re both agreeing with each other without even knowing it.
The majority of tech providers are doing some kind of ODM from a supplier, but the public facing brand gets all the credit. Instead of the real supplier. R&D and ODM partnerships are a lot different from what most of the public thinks.