Some people like to plant them during the cool months, while others wait until the early summer. Rose cuttings should be able to grow during any season. However, keep in mind that they'll need to be constantly watered, so if you plant them during the summer or live in a hot climate, they're going to dry out faster. For this reason, the rainy season might be your best option. Use a stick or pencil to make a hole in the soil for each of your rose cuttings that is 3–4 inches (7.6–10.2 cm) deep. You'll want to make sure the holes are wide enough that they won't wipe off the rooting hormone powder when you push the stems into the soil. Gently push the cutting down several inches into the soil, or half the length of the cutting. Once the cutting is in place, pat down the soil around the stem. For planting multiple cuttings, place them in rows 6–8 inches (15–20 cm) apart. The most important thing for successful rose cuttings is that they remain moist. Water them frequently, several times a day if the weather is warm, and this will help the roots flourish. To ensure that the moisture remains in the soil, you can place a plastic bag around the cutting once you’ve watered it. This creates a mini greenhouse for the roses. Keep an eye on the cuttings to make sure they’re never dried out, as well as to make sure the cuttings are taking root. You can test to see if the roots are growing by gently tugging on the cuttings. You should be able to feel a slight resistance after a week or 2, meaning the roots are growing well.

TL;DR in Vietnamese:
Giâm cành hoa hồng vào bất cứ thời điểm nào trong năm. Chọc một lỗ trong đất để cắm các cành hồng. Cắm các cành hồng xuống đất. Giữ ẩm cho các cành giâm. Theo dõi các cành giâm để đảm bảo chúng có đủ nước và mọc rễ.