I have been neglecting the Rossolimo for some time, so I thought I'd start by adding select games from the primary book. I'll start by simply inserting the games for my own convenience (the interface of flipping through games on chess.com is fantastic!), then come back for paraphrasing Palliser's specific analysis of each game, and ultimately return to give my own general analysis of the opening.

Game 44 (numbering based on order in the Bb5 Sicilian)

Game 45

Game 46

Game 47

Game 48

Game 49

Game 50

Game 51

What I have learned so far, regarding the fourth move alternative, 4. e5:

• White's goal is to exploit black's early movement of the knight to d5.
• The moment white castles, black gets more freedom of move choice because O-O is not a forcing move.
• If white captures on c6 with the bishop too soon, black's LSB gets freedom, meaning that black has more move alternatives.
• When the black knight is on d5, it threatens to capture on c3, should white play Nc3. Most of the time, this is not played for some reason, and Palliser does not mention this possibility. Perhaps the 'refutation' is obvious to him, but this detail must be explored.
• When white wants to delay Nc3 on move four (i.e. with 4. e5), white must include 3. ...g6 lines in his opening preparation.

Here are some examples:

Summary:

4. e5 is certainly playable, but allows black many possibilities. It seems like a solid sideline that leads to games where both sides will work towards exploiting the doubled pawns of the other side.

4. Bxc6 should be played, if white normally plays it against ...g6 lines anyway, for overlapping repetoires. Keep in mind that black has another choice with 5. ...Bg4, as seen in game 44, avoiding the transposition.

4. Qe2 is a flexible choice, shown in game 45.

Upon examining each resulting line, 4. Nc3 seems to force Qc7, which makes it one of the best choices in terms of opening preparation.

4. ...d6?! is a poor choice:

4. ...Nd4? is not much better, as seen in game 46:

4. ...e5 allows white to get the slight advantage, but apparently offers black good drawing chances. (game 48)

4. ...g6 allows white to push e5 and thus, is risky. However, black has more of a fighting chance. (game 47)

Thus, the main line is 4. ...Qc7!, eyeing e5. Black's plan is to clamp down on d4 with ...e5 and Nd4, which would make white's counterplay difficult.

5. O-O is straightforward: before further craziness ensues, white wants to have king safety to have a one-sided kinghunt.

5. ...Nd4 is mainline, and gives the knight a strong, central outpost while also attacking white's bishop.

5. ...a6!? is a promising alternative for black, which means Rossolimo players should prepare this line.

6. Re1, the mainline, prepares both e5 and Nd5.

6. Nxd4 is a more aggressive option (game 49):

6. ...a6 forces the bishop to move, and lets black wait a turn before showing his hand, in terms of development.

6. ...Nxb5?! allows white to seize the initiative:

6. ...e5 is playable.

Addenum:

Better response to 5. ...a6!?

Declining the gambit:

Taking the poisoned pawn: