If you have rJava installed already, try this, for example, 
Needs["RLink`"]
JLink`UninstallJava[]
InstallR["RHomeLocation" -> 
  "C:\\Data-Work\\Programs\\R-3.5.1\\App\\R-Portable",
 "NativeLibLocation" -> 
  "C:\\Data-Work\\Programs\\R-3.5.1\\App\\R-Portable\\library\\rJava\\\
jri\\x64"]
REvaluate["R.Version()"]
I'm using Window 10 (1803) and Mathematica 11.3.
"RHomeLocation" - path to your R and  "NativeLibLocation" - path to Java R Interface
see this for more details