or so vs roughly

or so and roughly both are adverbs.

Word	Noun	Adjective	Verb	Adverb
or so	No	No	No	Yes
roughly	No	No	No	Yes

As adverbs, or so and roughly are synonyms defined as:

or so and roughly: (of quantities) imprecise but fairly close to correct

Other synonyms of or so include about, approximately, around, close to, just about, more or less, some.

or so (adverb)	roughly (adverb)
(of quantities) imprecise but fairly close to correct	(of quantities) imprecise but fairly close to correct
	with rough motion as over a rough surface
	with roughness or violence (`rough' is an informal variant for `roughly')