Yes, the shape of our lips can affect the sounds we produce while speaking. Our lips, along with other speech organs such as the tongue, teeth, and vocal cords, play a crucial role in shaping the sounds we make. The study of these sounds is known as phonetics.
In the specific example you mentioned, "rose" and "roast," changing the shape of your lips can indeed alter the resulting sound. The word "rose" typically involves a rounded lip shape, while the word "roast" involves a slightly more open and spread lip shape. By adjusting the lip shape and position, you can modify the sound produced, potentially making "rose" sound more like "roast."
However, it's important to note that changing just the lip shape may not be sufficient to completely transform one word into another. Other articulatory features, such as the position of the tongue and the manner of airflow, also contribute to the distinct sounds of different words.
Additionally, context, intonation, and other phonetic factors also play a role in distinguishing between words, so solely changing the lip shape may not always result in a different word being perceived. The overall linguistic context and the listener's familiarity with the language are important factors in word recognition and understanding.