I'm going to be that guy again.
Rondon and Carroll are both 28. Signing either player would do nothing to rectify this massive problem we have where there are basically no peak age players in the squad. Neither has anywhere near the level of quality where a big short-term outlay would be worth it. I can see one of those two on loan, if their current club would allow it, but not on a permanent basis.
22-25 is the ideal range for a permanent signing (barring access to someone who is truly class, of course). Players that age have enough experience to contribute today but with room to go up a level.
The rot is only going to get worse if we keep spending on older players that don't really move the needle. Williams, Bolasie, Schneiderlin, Sigurdsson. What do we have to show for having brought that group to the club? Spending anything significant on Rondon or Carroll would be very much in the same vein.