Other than the function for the 'GUIDE' button being disabled after the code for the ROKU is entered, and having to place a strip of scotch tape along the side of the battery compartment lid, the Monster remote is not a bad inexpensive alternative solution for replacing two remote controls. Similar to the volume issue that use to exist with remote controls many years ago after entering a VCR code for many different brands of TVs.
Since the 'GUIDE' button works when using the original Samsung remote, it appears an incompatibility issue exists with the ROKU code that prevents the 'GUIDE' button from performing its function when in the TV mode.
The only function that does not work on the Monster remote is the "GUIDE" button when in the TV mode. I then entered the 2nd ROKU code (1992) for the 'AUX2' button. The remote now appears to work for the TV or when switched to the ROKU. When the light went out, the code was saved. Finished this step by entering the 1st of the two 4-digit ROKU codes (1966) into the remote. Then pressed and held the 'SET' button until its light illuminated and was steady. So I pressed the 'AUX1' button and after it flashed, released it. The next step was to manually enter the 4-digit code for the ROKU. The remote was then used to turn on the TV and EVERY button performed its function. I continued to press the buttons until the TV turned off which indicated a code had been found and stored. After a couple seconds, the buttons started to flash which indicated a code was being accessed. When the light flashed once, I continued to press the two buttons. The approach I tried was to first perform an automatic brand search for the TV by pressing the 'TV' button on the remote, and while depressed, pressing the '4' button which correlates to Samsung TVs from a table provided in the instructions for the remote. Therefore, decided to try a hybrid approach. However, I did not want to spend the time trying each of the 24 possible combinations. Since two of the four ROKU codes under 'STREAMING PLAYER' were also listed under 'VIDEO-ACCESSORY in the reference sheet, I decided not to try those two codes which reduced the total number of possible code combinations to 24. Therefore, a compatibility issue appears to exist between my Samsung TV and ROKU Express when manually entering the codes. When the Samsung code was re-entered for the TV, the remote was prevented from performing functions for the ROKU. When manually entering the code first for the Samsung TV, followed by manually entering the code for the ROKU, the code for the ROKU would prevent the remote from performing functions for the TV. Thanks to Tivoburkee stating "The Express or any stand alone Roku would not respond to the Roku tv IR code, they are completely different.", I decided to attempt a different approach other than manually entering the 48 possible combinations from the 4 ROKU codes that each worked when manually entered separately, and the 12 different Samsung TV codes that each worked when manually entered separately.
Believe I have figured out how to make the Monster remote work with a Samsung TV utilizing an antenna and a ROKU via a wireless connection.