How does one stop using rowwise in dplyr?

As found in the comments and the other answer, the correct way of doing this is to use ungroup().

The operation rowwise(df) sets one of the classes of df to be rowwise_df. We can see the methods on this class by examining the code here, which gives the following ungroup method:

#' @export
ungroup.rowwise_df <- function(x) {
  class(x) <- c( "tbl_df", "data.frame")
  x
}

So we see that ungroup is not strictly removing a grouped structure, instead it just removes the rowwise_df class added from the rowwise function.

Just use ungroup()

The following produces a warning:

data.frame(a=1:4) %>% rowwise() %>% 
  group_by(a)
#Warning message:
#Grouping rowwise data frame strips rowwise nature

This does not produce the warning:

data.frame(a=1:4) %>% rowwise() %>% 
  ungroup() %>% 
  group_by(a)

You can use as.data.frame(), like below

> data.frame(a=1:4) %>% rowwise() %>% group_by(a)
# A tibble: 4 x 1
# Groups:   a [4]
      a
* <int>
1     1
2     2
3     3
4     4
Warning message:
Grouping rowwise data frame strips rowwise nature 

> data.frame(a=1:4) %>% rowwise() %>% as.data.frame() %>% group_by(a)
# A tibble: 4 x 1
# Groups:   a [4]
      a
* <int>
1     1
2     2
3     3
4     4