Importing raster with R from File Geodatabase?

R spatial packages all depend on GDAL for file read/write, and GDAL uses the OpenFileGDB driver, which can only read vector data sources at this time - see https://www.gdal.org/drv_openfilegdb.html. The driver provides no write access at all.

If you have a recent version of ArcMap (>=10.3.1) or ArcGis Pro (1.1) installed, you can use the R package arcgisbinding to connect to ESRI proprietary data sources. This allows read/write access to anything in a File Geodatabase, plus SDE connections, as well as conversion from ESRI's own take on R spatial objects to and from sf, sp, and raster style objects. See https://github.com/R-ArcGIS/r-bridge.