Ni devas izoli la ĉambron.

Because -as is the Esperanto ending for the present tense.

• devi = to have to / must
• devas = have to / must
• devis = had to
• devos = will have to

So Ni devas izoli la ĉambron literally has the structure We must isolate the room.

The ending -i marks the infinitive, the basic dictionary form of a verb: to isolate.

After devas, Esperanto normally uses an infinitive:

• Mi devas iri = I must go
• Ŝi devas labori = She must work
• Ni devas izoli la ĉambron = We must isolate the room

So devas is the conjugated verb, and izoli stays in the infinitive form.

The -n ending marks the direct object in Esperanto.

Here, la ĉambro is the thing being isolated, so it becomes:

• la ĉambro = the room
• la ĉambron = the room (as a direct object)

This is very common in Esperanto:

• Mi vidas la hundon = I see the dog
• Ni purigas la domon = We clean the house
• Ni devas izoli la ĉambron = We must isolate the room

La is the definite article and means the.

So:

• ĉambro = a room / room
• la ĉambro = the room

In your sentence, la ĉambron means the room as the object.

If you said Ni devas izoli ĉambron, that would sound more like We must isolate a room or some room, which is less specific.

Yes. Izoli is a normal verb, and it is transitive, which means it can take a direct object.

So you can say:

• izoli la ĉambron = isolate the room
• izoli la pacienton = isolate the patient

Because it is transitive, the noun after it gets the -n object ending.

Yes, Esperanto word order is fairly flexible because the -n ending shows the object.

The most neutral order is:

• Ni devas izoli la ĉambron.

But other orders are possible for emphasis, such as:

• La ĉambron ni devas izoli.

That puts more emphasis on the room.

Even so, beginners should usually stick with the standard order: subject + verb + infinitive + object.

Usually ni means we, and it can include the speaker plus one or more other people. Whether it includes the listener depends on context, just like English we.

So Ni devas izoli la ĉambron could mean:

• the speaker and the listener must isolate the room, or
• the speaker and some other group must isolate the room

Esperanto does not have separate everyday words for inclusive we and exclusive we.

Ĉ is pronounced like ch in church.

So:

• ĉambro sounds roughly like CHAHM-bro
• ĉambron is CHAHM-bron

A few other pronunciation notes:

• c alone sounds like ts
• j sounds like English y
• z sounds like English z
• stress usually falls on the second-to-last syllable

So ĉambron is stressed on ĉam: ĈAM-bron.

It is often translated as must or have to, but the exact tone depends on context.

• Ni devas izoli la ĉambron can mean We must isolate the room
• It can also feel like We have to isolate the room

In many cases, Esperanto devi covers both ideas, and context tells you whether it is an obligation, necessity, rule, or strong recommendation.

Because izoli takes a direct object directly, without a preposition.

In English, some verbs need a preposition, and some do not. Esperanto works similarly, but you learn it verb by verb.

Here it is simply:

• izoli ion = to isolate something

So:

• Ni devas izoli la ĉambron

No preposition is needed.

The plural ending in Esperanto is -j.

So:

• ĉambro = room
• ĉambroj = rooms

If it is also a direct object, you add -n too:

• la ĉambrojn = the rooms

Example:

• Ni devas izoli la ĉambrojn = We must isolate the rooms

So the order of endings is:

noun + plural -j + object -n

Yes, grammatically you can. But it changes the meaning.

• Ni devas izoli la ĉambron = We must isolate the room
• Ni devas izoli ĉambron = We must isolate a room / some room

Esperanto has no separate word for English a/an, so the bare noun often has that indefinite meaning.

Only normal sentence capitalization. Ni is capitalized because it is the first word of the sentence.

Otherwise it would be lowercase:

• ni = we

Esperanto does not capitalize pronouns like English I. So in the middle of a sentence, you would write ni, not Ni.