Yes you will need to, but you will have a huge licensing cost on your hands if you do not have unlimited virtualisation rights or are using physical tin. As each new server you spin up for SSRS needs to be licensed individually. So thats 5 lots of servers needing 5 lots of licenses, so thats at least a minimum of 20 cores of Enterprise licensing needed which is a hefty chunk of change.
The other option is to have 1 SSRS instance and split the root folder out into 4 folders and deploy to those and set permissions accordingly.
Server\SSRS - 4 folders at root Data1, Data2, Data3, Data4 permissions set as needed and deploy reports for the specifics to the right folder.
There really is no need to have multiple SSRS instances any more unless you hit compute issues and need to split the load but then I would look at scale out deployments over multi instances.