I think it's partly owned as Xiaomi invested in Roborock back in 2014.Beijing Roborock Technology Co. Ltd. is not a Xiaomi subsidiary. It is an independent company owned by Chang Jing which is part of Xiaomi's ecological chain, i.e. an ecosystem of companies which have been helped or backed or partnered in some way by Xiaomi during their growth phase. The car venture is known as ROX Motor.
Shanghai ROX Intelligent Technology Co., Ltd. is an affiliate of Roborock which is in charge of the car project. It has three subsidiaries, of which two, Anhui ROX Automobile Technology Co., Ltd. and Anhui ROX Automobile Manufacturing Co., Ltd. would be responsible for the technical development and manufacturing of vehicles, respectively. The third is a sales company.