The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of sub-orbital rocket payloads that will aim to make large field-of-view spectroscopic observations of diffuse soft X-ray astrophysical objects. The tREXS payloads will passively focus X-rays onto a co-Aligned array of reflection gratings, dispersing the incident X-rays onto a focal plane camera. The large focal plane requires the detector to cover a large area (100s of mm), have good quantum efficiency across the soft X-ray energy range (300 eV to 1000 eV), and survive the high-stress environment of a sub-orbital rocket launch. This paper will look at the options that were considered for this focal plane detector including Micro-Channel Plates, Charge-Coupled Devices, and CMOS detectors; including the use of commercially available camera solutions from companies such as Andor. The final choice for the focal plane camera will then be discussed in detail including the ultimate decisions behind the choice, system level integration into the payload design, and the requirements on the readout electronics, telemetry interface, and power.