Bengals have had success in the late rounds and UDFA signings

The past three seasons, the Bengals have had mixed results in both the early (1-2) and middle rounds (3-4) of the NFL Draft. However, they have done well building their core in later rounds (5-7) and with their horde of undrafted free agent signings. A summary:

2012

Fifth round: Starting wide receiver Marvin Jones and starting safety George Iloka.
Sixth round: Running back Dan "Boom" Herron, who is on the Colts roster as a productive third back (he's done significantly better than Trent Richardson); Cincinnati also signed Oakland's sixth-round pick, defensive tackle Christo Bilukidi, if you want to count him.
Seventh round: Pick was part of a conditional package that sent cornerback David Jones to Jacksonville in exchange for starting safety Reggie Nelson. 
UDFA: Starting linebackers Vontaze Burfict and Emmanuel Lamur, practice squad center (and former roster member) Trevor Robinson.

2013

Fifth round: Backup offensive lineman Tanner Hawkinson.
Sixth round: Backup running back and special teamer Rex Burkhead, practice squad receiver Cobi Hamilton.
Seventh round: Pick was part of a conditional package that was part of Cincinnati's acquisition for safety and special teamer Taylor Mays. 
Seventh round: Offensive tackle Reid Fragel, who was on the Browns roster as the second-string RT last year before cutting him this year; backup offensive guard T.J. Johnson.
UDFA: Special teams ace Jayson DiManche, practice squad cornerback Onterio McCalebb.

2014

Fifth round: Backup quarterback A.J. McCarron.
Sixth round: Linebacker and special teamer Marquis Flowers.
Seventh round: backup receiver and special teamer James Wright (cornerback Lavelle Westbrooks got off to a good start but eventually got put on IR).
UDFA: Starting H-back Ryan Hewitt, offensive guard Trey Hopkins (currently on IR), practice squad running back James Wilder, practice squad receiver Colin Lockett, practice squad offensive guard Dan France.