The roll-to-roll (R2R) process is an important high throughput and low cost manufacturing method in which additive processes can be used to create structures and devices in a continuous manner. In particular, the use of a flexible polymer substrate with a conductive ink patterned on the surface can enable flexible electronics and the fabrication of R2R printed electronics allows the mass production of various microelectronic products. This research investigated a continuous R2R flexographic printing process on a highly filled and flexible substrate created from polymeric materials. The substrate was prepared from low-density polyethylene (LDPE) and a ferroelectric filler, barium strontium titanate (BST). The role of the ferroelectric filler is to enhance the electrical properties of the substrate, which are essential for printed electronics. The use of a ferroelectric filler allows for tailoring of the dielectric constant by the filler loading and applied bias, which gives the substrate tunability. An appropriate ink must be selected for compatibility with the substrate in terms of adhesion and curing. A suitable conductive ink with a minimum silver content of 50% was used for printing. The curing time of the ink depends on parameters, such as heat, the type of ink, the type of substrate, and the number of layers. Accordingly, the curing process parameters were optimized for the LDPE/BST substrate. The factors for printing in the R2R process were feature size, repeatability of the pattern, the speed of the printing line, and the flexibility of the substrate under tension and heat. The results for R2R printing of flexible electronic devices are critically discussed.