Please see https://merck.github.io/r2rtf/articles/index.html for the full documentation. Here is only a minimal example:
library(dplyr)
library(r2rtf)
head(iris) %>%
rtf_body() %>% # Step 1 Add attributes
rtf_encode() %>% # Step 2 Convert attributes to RTF encode
write_rtf(file = "ex-tbl.rtf") # Step 3 Write to a .rtf file