There is no significant definitional difference between the three expressions, but they differ in connotation, so they cannot exactly be used interchangeably either.
"To take a role" is a neutral expression, which can be used in a variety of ways but usually serves as a denotation that implies nothing else. It doesn't seem like what you're looking for.
"To take over a role" is, as you said, to take a role that was previously occupied by somebody else, which seems to be what you're looking for, as your colleague "replaced" another worker, so he "took over" that worker's role.
"To take on a role" is, again as you said, to accept the role as a challenge. However, you seem to be emphasizing the replacement aspect more than the challenge aspect, at least from what I can tell by your description.
I'd personally recommend "take over the role".
The Einstein macro is a fake. It is an example of comedic fake quotes such as "You can't trust everything you read on the internet" - Abraham Lincoln. This quote is purely about League of Legends (abbreviated to LoL).
Essentially the answer above me explains how 'Mid or Feed' applies to LoL.
People say mid or feed to bully their team into getting the lane than they prefer to play. Mid lane is usually the lane where people can become most powerful but other lanes need to be played as well.
Saying 'Mid or Feed' is frowned upon because as a team game LoL works best when on player doesn't bully his own team.
Best Answer
That is what it actually means. Take it while eating a meal, or after you have already started eating the meal. The idea is not to take it on an empty stomach. (Note this is not medical advice and you should consult your doctor if you have questions about the prescription or nonprescription medicine.)
Some medicines may upset an empty stomach. Some medicines may work too quickly if taken on an empty stomach. For the same reason, doctors may prescribe some medicines to be taken on an empty stomach.
Some medicines interfere with the work of other medicines, and so they shouldn't be taken within two hours of each other.