There are many rosewoods. The properties vary widely. The appearance and color varies widely and the species cannot always be identified from the look at the side of a board. Many can guess, few will KNOW without more info.
Scrape a bit and take a sniff - many rosewoods have distinctive smells. That might not identify it for you but might help someone else with experience. Ask other woodturners for opinions. Many have experience with the look. I have dozens of rosewood species and might be able to compare it to one with a name on it. Be aware that many dealers have no clue and write a wood name based on a guess.
To narrow it down, first measure and weigh the piece and compare the density numbers on the Wood Database.
Using a single edge razor blade, shave off a small area of endgrain, enough to show at least two rings. Look at the endgrain through a magnifier - 10x is recommended but I prefer a low-power stereo microscope. Determine if the wood is ring porous, semi diffuse porous, or diffuse porous. Look for rays and note the width of the rays. Note the relative size of the earlywood pores compared to the latewood. Check the large earlywood pores - are they open (hollow like soda straws), filled with sparkly "tyloses", or something else. Those of Cocobolo and some other rosewoods are filled with what looks like a hard or waxy substance, sometimes colored orange.
Read this articles, paying special attention to section 7. Compare what you see in the end grain to the photos of candidate species in the Wood Database. Be aware that it is FAR easier to get a positive ID on domestic species than the many thousands of possible exotics.
If all else fails, look at the last section. You can send a small sample to the gov lab and they will make an ID for no charge.
If interested in learning more, I recommend the book "Identifying Wood" by R. Bruce Hoadley.
JKJ