The most common and most likely answer to this crossword clue is the 10 letter word SKETCHIEST
I've seen this crossword clue in Financial Times
S
K
E
T
C
H
I
E
S
T
Buddy explains!
The straight part
We know that "Roughest" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case roughest = sketchiest.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SKETCHIEST mean?
SKETCHIEST adjective- Roughly or hastily laid out; intended for later refinement.
- Resembling a comedy sketch, of sketch quality.
- Of questionable or doubtful quality.
- (of a person) Suspected of taking part in illicit or dishonorable dealings.
- (of a person) Disturbing or unnerving, often in such a way that others may suspect them of intending physical or sexual harm or harassment.