Dont buy heads from
sign in global,they are all either scams or 'refubished; - you can't refurbish the heads. All they do is clean the outside of non working heads. Only buy a proper new head from someone with a good reputation in the US ( and not from Digiprint! )
The caps are also cheap chinese copies and Rolands are pretty sensitive to these,so buy OEM ones as well as dampers.
If the fuses and transistors are fine then it is most likely the head is firing, but completely blocked so no ink will come out.
If you can do all the work yourself you are looking at around $3000 - $3500 in parts and new inks so it depends if it is worth it to you. I hope you didn't pay more than $500 for the printer as that is all it is worth at the moment