Yes, regardless if you are using a pre-certified module/parts or not you need to CE certify your product as a whole. However if you use pre-certified modules the testing is cheaper/less complicated.

I do my certification testing in China by a reputable lab which is much cheaper than doing it here in Switzerland (at least 15k USD). At a minimum expect to spend 1000-2000 USD if all goes well.

There is a workaround for CE but it's a bit of a dirty trick. If you are not expecting to sell very many and your target audience are tinkerers then you can sell your device as a kit. There must be assembly that the end user has to do but they are then the ones "putting the device into the market" and they take on that responsivity of CE. That basically means they can't sell it unless they get a CE. Such an example is https://www.clockworkpi.com/ which sell their products a kits.