AFAIK isso deve fazer o trabalho:
^(?i)(?=.*mktg)((?!round|smp).)*$
Explicação:
^ : beginning of line
(?i) : case insensitive
(?= : start lookahead, zero-length assertion, make sure we have
.* : 0 or more any character
mktg : literally "mktg"
) : end lookahead
( : start group
(?! : start negative lookahead, zero-length assertion, make we DON'T have:
round : literally "round"
| : OR
smp : literally "smp"
) : end lookahead
. : any character
)* : group must be repeated 0 or more times
$ : end of line
Casos de teste:
Match: mktg
Match: abc mktg xyz
No match: round mktg
No match: SmP mktg
No match: SPM ROUND