The metre requires a syllable; the 2nd folio reads to.
"But with such words that are but roated in."
'Roated' is probably roted; but no such verb occurs elsewhere as rote. Boswell proposed rooted.
"Not only what is dangerous present but
The loss of what is past."
There can be little doubt that only was the word omitted.
"Often thus; which correcting thy stout heart,