Cognition and behaviour rely on coordinated activity from neural circuits distributed across three dimensions. However, typical probes for recording neural activity in the brain are limited to two-dimensional interfacing due to the planar semiconductor fabrication process. Here we report a rolling-of-soft-electronics approach to create monolithic three-dimensional (3D) neural probes with high scalability and design flexibility. Compared with previous stacking or assembly methods, the approach directly transforms a planar device into a 3D probe by leveraging the softness of flexible electrodes. The electrode shanks are initially fabricated in a single plane and then connected to a flexible spacer. By varying the features of planar design, such as shank pitch and spacer layer thickness, the device can then be deterministically rolled into versatile 3D probe designs containing hundreds of electrodes. With the system, we demonstrate single-unit spike recording in vivo in rodent and non-human primate models. We also show that the probe can provide microscopy-like 3D spatiotemporal mapping of spike activities in the rodent visual cortex, with five-week-long recording stability and promising 3D decoding performance of visual orientation.